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	$186.43	13.418%	$211.4452	$211.45	$211.45	$211.40
Purchase #2	$131.81	4.474%	$137.7072	$137.71	$137.70	$137.70
Purchase #3	$80.33	7.410%	$86.2825	$86.28	$86.30	$86.30
Purchase #4	$174.69	7.118%	$187.1244	$187.12	$187.10	$187.10
Purchase #5	$175.66	11.628%	$196.0857	$196.09	$196.10	$196.10
Purchase #6	$24.52	12.233%	$27.5195	$27.52	$27.50	$27.50
Purchase #7	$152.46	7.114%	$163.306	$163.31	$163.30	$163.30
7 purchase totals =	$925.90		$1,009.4705	$1,009.48	$1,009.45	$1,009.40