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	$178.50	7.176%	$191.3092	$191.31	$191.30	$191.30
Purchase #2	$38.70	9.413%	$42.3428	$42.34	$42.35	$42.30
Purchase #3	$120.71	13.203%	$136.6473	$136.65	$136.65	$136.60
Purchase #4	$211.87	3.388%	$219.0482	$219.05	$219.05	$219.00
Purchase #5	$108.90	8.852%	$118.5398	$118.54	$118.55	$118.50
Purchase #6	$131.60	12.734%	$148.3579	$148.36	$148.35	$148.40
Purchase #7	$157.48	13.760%	$179.1492	$179.15	$179.15	$179.10
7 purchase totals =	$947.76		$1,035.3944	$1,035.40	$1,035.40	$1,035.20