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	$148.67	12.808%	$167.7117	$167.71	$167.70	$167.70
Purchase #2	$42.96	13.700%	$48.8455	$48.85	$48.85	$48.80
Purchase #3	$48.83	3.407%	$50.4936	$50.49	$50.50	$50.50
Purchase #4	$35.31	6.262%	$37.5211	$37.52	$37.50	$37.50
Purchase #5	$78.86	10.714%	$87.3091	$87.31	$87.30	$87.30
Purchase #6	$120.98	3.785%	$125.5591	$125.56	$125.55	$125.60
Purchase #7	$40.28	9.478%	$44.0977	$44.10	$44.10	$44.10
7 purchase totals =	$515.89		$561.5378	$561.54	$561.50	$561.50