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	$91.45	11.536%	$101.9997	$102.00	$102.00	$102.00
Purchase #2	$77.85	5.578%	$82.1925	$82.19	$82.20	$82.20
Purchase #3	$137.90	12.870%	$155.6477	$155.65	$155.65	$155.60
Purchase #4	$35.31	5.832%	$37.3693	$37.37	$37.35	$37.40
Purchase #5	$17.74	6.577%	$18.9068	$18.91	$18.90	$18.90
Purchase #6	$226.93	11.718%	$253.5217	$253.52	$253.50	$253.50
Purchase #7	$55.63	10.581%	$61.5162	$61.52	$61.50	$61.50
7 purchase totals =	$642.81		$711.1539	$711.16	$711.10	$711.10