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	$61.60	9.597%	$67.5118	$67.51	$67.50	$67.50
Purchase #2	$162.34	13.304%	$183.9377	$183.94	$183.95	$183.90
Purchase #3	$179.78	9.360%	$196.6074	$196.61	$196.60	$196.60
Purchase #4	$83.49	8.874%	$90.8989	$90.90	$90.90	$90.90
Purchase #5	$36.79	3.313%	$38.0089	$38.01	$38.00	$38.00
Purchase #6	$57.96	11.376%	$64.5535	$64.55	$64.55	$64.60
Purchase #7	$41.55	6.829%	$44.3874	$44.39	$44.40	$44.40
7 purchase totals =	$623.51		$685.9056	$685.91	$685.90	$685.90