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	$204.87	9.243%	$223.8061	$223.81	$223.80	$223.80
Purchase #2	$43.97	10.452%	$48.5657	$48.57	$48.55	$48.60
Purchase #3	$182.60	5.312%	$192.2997	$192.30	$192.30	$192.30
Purchase #4	$78.48	10.535%	$86.7479	$86.75	$86.75	$86.70
Purchase #5	$111.73	13.560%	$126.8806	$126.88	$126.90	$126.90
Purchase #6	$141.89	5.347%	$149.4769	$149.48	$149.50	$149.50
Purchase #7	$196.32	13.494%	$222.8114	$222.81	$222.80	$222.80
7 purchase totals =	$959.86		$1,050.5883	$1,050.60	$1,050.60	$1,050.60