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	$83.37	4.155%	$86.834	$86.83	$86.85	$86.80
Purchase #2	$158.77	11.574%	$177.146	$177.15	$177.15	$177.10
Purchase #3	$131.25	13.443%	$148.8939	$148.89	$148.90	$148.90
Purchase #4	$9.36	4.450%	$9.7765	$9.78	$9.80	$9.80
Purchase #5	$53.86	11.639%	$60.1288	$60.13	$60.15	$60.10
Purchase #6	$134.95	13.287%	$152.8808	$152.88	$152.90	$152.90
Purchase #7	$61.62	10.191%	$67.8997	$67.90	$67.90	$67.90
7 purchase totals =	$633.18		$703.5597	$703.56	$703.65	$703.50