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	$95.71	10.569%	$105.8256	$105.83	$105.85	$105.80
Purchase #2	$213.42	13.444%	$242.1122	$242.11	$242.10	$242.10
Purchase #3	$74.61	5.183%	$78.477	$78.48	$78.50	$78.50
Purchase #4	$179.36	5.221%	$188.7244	$188.72	$188.70	$188.70
Purchase #5	$229.83	5.830%	$243.2291	$243.23	$243.25	$243.20
Purchase #6	$137.29	3.565%	$142.1844	$142.18	$142.20	$142.20
Purchase #7	$244.58	3.778%	$253.8202	$253.82	$253.80	$253.80
7 purchase totals =	$1,174.80		$1,254.3729	$1,254.37	$1,254.40	$1,254.30