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	$199.93	5.600%	$211.1261	$211.13	$211.15	$211.10
Purchase #2	$48.99	13.681%	$55.6923	$55.69	$55.70	$55.70
Purchase #3	$203.81	11.313%	$226.867	$226.87	$226.85	$226.90
Purchase #4	$131.26	6.145%	$139.3259	$139.33	$139.35	$139.30
Purchase #5	$87.78	5.136%	$92.2884	$92.29	$92.30	$92.30
Purchase #6	$139.74	8.425%	$151.5131	$151.51	$151.50	$151.50
Purchase #7	$126.86	3.306%	$131.054	$131.05	$131.05	$131.10
7 purchase totals =	$938.37		$1,007.8668	$1,007.87	$1,007.90	$1,007.90