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	$75.65	10.182%	$83.3527	$83.35	$83.35	$83.40
Purchase #2	$237.78	12.423%	$267.3194	$267.32	$267.30	$267.30
Purchase #3	$95.72	13.696%	$108.8298	$108.83	$108.85	$108.80
Purchase #4	$91.55	8.338%	$99.1834	$99.18	$99.20	$99.20
Purchase #5	$211.41	5.352%	$222.7247	$222.72	$222.70	$222.70
Purchase #6	$83.72	6.718%	$89.3443	$89.34	$89.35	$89.30
Purchase #7	$135.57	11.474%	$151.1253	$151.13	$151.15	$151.10
7 purchase totals =	$931.40		$1,021.8796	$1,021.87	$1,021.90	$1,021.80