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	$232.32	9.373%	$254.0954	$254.10	$254.10	$254.10
Purchase #2	$89.35	11.484%	$99.611	$99.61	$99.60	$99.60
Purchase #3	$54.86	7.551%	$59.0025	$59.00	$59.00	$59.00
Purchase #4	$240.75	12.819%	$271.6117	$271.61	$271.60	$271.60
Purchase #5	$240.92	11.708%	$269.1269	$269.13	$269.15	$269.10
Purchase #6	$50.63	6.634%	$53.9888	$53.99	$54.00	$54.00
Purchase #7	$113.78	12.804%	$128.3484	$128.35	$128.35	$128.30
7 purchase totals =	$1,022.61		$1,135.7847	$1,135.79	$1,135.80	$1,135.70