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	$177.82	10.318%	$196.1675	$196.17	$196.15	$196.20
Purchase #2	$124.54	11.187%	$138.4723	$138.47	$138.45	$138.50
Purchase #3	$191.67	6.449%	$204.0308	$204.03	$204.05	$204.00
Purchase #4	$197.61	5.500%	$208.4786	$208.48	$208.50	$208.50
Purchase #5	$224.90	7.760%	$242.3522	$242.35	$242.35	$242.40
Purchase #6	$26.87	6.445%	$28.6018	$28.60	$28.60	$28.60
Purchase #7	$53.45	11.717%	$59.7127	$59.71	$59.70	$59.70
7 purchase totals =	$996.86		$1,077.8159	$1,077.81	$1,077.80	$1,077.90