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	$151.47	8.714%	$164.6691	$164.67	$164.65	$164.70
Purchase #2	$99.90	6.224%	$106.1178	$106.12	$106.10	$106.10
Purchase #3	$42.50	3.846%	$44.1346	$44.13	$44.15	$44.10
Purchase #4	$130.99	10.479%	$144.7164	$144.72	$144.70	$144.70
Purchase #5	$84.89	5.637%	$89.6752	$89.68	$89.70	$89.70
Purchase #6	$99.51	10.595%	$110.0531	$110.05	$110.05	$110.10
Purchase #7	$82.94	7.664%	$89.2965	$89.30	$89.30	$89.30
7 purchase totals =	$692.20		$748.6627	$748.67	$748.65	$748.70