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	$71.34	4.730%	$74.7144	$74.71	$74.70	$74.70
Purchase #2	$226.64	13.854%	$258.0387	$258.04	$258.05	$258.00
Purchase #3	$112.61	5.707%	$119.0367	$119.04	$119.05	$119.00
Purchase #4	$82.46	8.315%	$89.3165	$89.32	$89.30	$89.30
Purchase #5	$195.85	10.403%	$216.2243	$216.22	$216.20	$216.20
Purchase #6	$247.89	3.437%	$256.41	$256.41	$256.40	$256.40
Purchase #7	$136.68	11.620%	$152.5622	$152.56	$152.55	$152.60
7 purchase totals =	$1,073.47		$1,166.3028	$1,166.30	$1,166.25	$1,166.20