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	$5.34	10.774%	$5.9153	$5.92	$5.90	$5.90
Purchase #2	$227.74	7.707%	$245.2919	$245.29	$245.30	$245.30
Purchase #3	$242.72	13.813%	$276.2469	$276.25	$276.25	$276.20
Purchase #4	$101.58	9.580%	$111.3114	$111.31	$111.30	$111.30
Purchase #5	$205.74	13.648%	$233.8194	$233.82	$233.80	$233.80
Purchase #6	$97.95	12.563%	$110.2555	$110.26	$110.25	$110.30
Purchase #7	$56.67	4.392%	$59.1589	$59.16	$59.15	$59.20
7 purchase totals =	$937.74		$1,041.9993	$1,042.01	$1,041.95	$1,042.00