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	$106.67	10.840%	$118.233	$118.23	$118.25	$118.20
Purchase #2	$182.54	7.838%	$196.8475	$196.85	$196.85	$196.80
Purchase #3	$99.66	12.156%	$111.7747	$111.77	$111.75	$111.80
Purchase #4	$20.64	8.717%	$22.4392	$22.44	$22.45	$22.40
Purchase #5	$87.28	8.597%	$94.7835	$94.78	$94.80	$94.80
Purchase #6	$88.97	11.187%	$98.9231	$98.92	$98.90	$98.90
Purchase #7	$37.67	11.846%	$42.1324	$42.13	$42.15	$42.10
7 purchase totals =	$623.43		$685.1334	$685.12	$685.15	$685.00