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	$84.57	10.145%	$93.1496	$93.15	$93.15	$93.10
Purchase #2	$63.27	11.361%	$70.4581	$70.46	$70.45	$70.50
Purchase #3	$167.46	9.632%	$183.5897	$183.59	$183.60	$183.60
Purchase #4	$139.55	8.515%	$151.4327	$151.43	$151.45	$151.40
Purchase #5	$93.48	7.621%	$100.6041	$100.60	$100.60	$100.60
Purchase #6	$111.66	13.142%	$126.3344	$126.33	$126.35	$126.30
Purchase #7	$223.39	8.741%	$242.9165	$242.92	$242.90	$242.90
7 purchase totals =	$883.38		$968.4851	$968.48	$968.50	$968.40