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	$16.94	3.580%	$17.5465	$17.55	$17.55	$17.50
Purchase #2	$71.62	5.300%	$75.4159	$75.42	$75.40	$75.40
Purchase #3	$33.81	10.525%	$37.3685	$37.37	$37.35	$37.40
Purchase #4	$122.92	3.438%	$127.146	$127.15	$127.15	$127.10
Purchase #5	$92.96	6.473%	$98.9773	$98.98	$99.00	$99.00
Purchase #6	$94.71	10.191%	$104.3619	$104.36	$104.35	$104.40
Purchase #7	$98.46	10.592%	$108.8889	$108.89	$108.90	$108.90
7 purchase totals =	$531.42		$569.7050	$569.72	$569.70	$569.70