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	$163.87	4.241%	$170.8197	$170.82	$170.80	$170.80
Purchase #2	$239.29	12.757%	$269.8162	$269.82	$269.80	$269.80
Purchase #3	$225.38	13.645%	$256.1331	$256.13	$256.15	$256.10
Purchase #4	$121.83	12.623%	$137.2086	$137.21	$137.20	$137.20
Purchase #5	$154.64	13.114%	$174.9195	$174.92	$174.90	$174.90
Purchase #6	$161.33	13.398%	$182.945	$182.95	$182.95	$182.90
Purchase #7	$229.64	11.280%	$255.5434	$255.54	$255.55	$255.50
7 purchase totals =	$1,295.98		$1,447.3855	$1,447.39	$1,447.35	$1,447.20