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	$237.44	4.258%	$247.5502	$247.55	$247.55	$247.60
Purchase #2	$46.55	7.532%	$50.0561	$50.06	$50.05	$50.10
Purchase #3	$32.85	8.119%	$35.5171	$35.52	$35.50	$35.50
Purchase #4	$229.49	6.313%	$243.9777	$243.98	$244.00	$244.00
Purchase #5	$75.83	3.800%	$78.7115	$78.71	$78.70	$78.70
Purchase #6	$246.60	7.269%	$264.5254	$264.53	$264.55	$264.50
Purchase #7	$199.63	12.831%	$225.2445	$225.24	$225.25	$225.20
7 purchase totals =	$1,068.39		$1,145.5825	$1,145.59	$1,145.60	$1,145.60