Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$131.44	12.644%	$148.0593	$148.06	$148.05	$148.10
Purchase #2	$163.71	8.270%	$177.2488	$177.25	$177.25	$177.20
Purchase #3	$175.56	12.165%	$196.9169	$196.92	$196.90	$196.90
Purchase #4	$132.78	13.367%	$150.5287	$150.53	$150.55	$150.50
Purchase #5	$167.44	4.802%	$175.4805	$175.48	$175.50	$175.50
Purchase #6	$136.68	11.542%	$152.4556	$152.46	$152.45	$152.50
Purchase #7	$220.81	3.337%	$228.1784	$228.18	$228.20	$228.20
7 purchase totals =	$1,128.42		$1,228.8682	$1,228.88	$1,228.90	$1,228.90