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	$147.53	11.442%	$164.4104	$164.41	$164.40	$164.40
Purchase #2	$141.45	9.799%	$155.3107	$155.31	$155.30	$155.30
Purchase #3	$84.74	12.549%	$95.374	$95.37	$95.35	$95.40
Purchase #4	$116.28	12.169%	$130.4301	$130.43	$130.45	$130.40
Purchase #5	$175.93	7.315%	$188.7993	$188.80	$188.80	$188.80
Purchase #6	$242.52	4.578%	$253.6226	$253.62	$253.60	$253.60
Purchase #7	$173.91	6.668%	$185.5063	$185.51	$185.50	$185.50
7 purchase totals =	$1,082.36		$1,173.4534	$1,173.45	$1,173.40	$1,173.40