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	$103.85	7.347%	$111.4799	$111.48	$111.50	$111.50
Purchase #2	$101.87	13.327%	$115.4462	$115.45	$115.45	$115.40
Purchase #3	$137.63	13.302%	$155.9375	$155.94	$155.95	$155.90
Purchase #4	$130.47	10.263%	$143.8601	$143.86	$143.85	$143.90
Purchase #5	$175.99	6.590%	$187.5877	$187.59	$187.60	$187.60
Purchase #6	$209.64	13.825%	$238.6227	$238.62	$238.60	$238.60
Purchase #7	$159.74	12.478%	$179.6724	$179.67	$179.65	$179.70
7 purchase totals =	$1,019.19		$1,132.6065	$1,132.61	$1,132.60	$1,132.60