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	$128.60	10.106%	$141.5963	$141.60	$141.60	$141.60
Purchase #2	$222.64	6.846%	$237.8819	$237.88	$237.90	$237.90
Purchase #3	$67.51	5.446%	$71.1866	$71.19	$71.20	$71.20
Purchase #4	$140.58	6.818%	$150.1647	$150.16	$150.15	$150.20
Purchase #5	$147.61	5.550%	$155.8024	$155.80	$155.80	$155.80
Purchase #6	$35.79	4.809%	$37.5111	$37.51	$37.50	$37.50
Purchase #7	$96.73	5.248%	$101.8064	$101.81	$101.80	$101.80
7 purchase totals =	$839.46		$895.9494	$895.95	$895.95	$896.00