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	$69.56	4.150%	$72.4467	$72.45	$72.45	$72.40
Purchase #2	$161.74	6.482%	$172.224	$172.22	$172.20	$172.20
Purchase #3	$10.40	4.502%	$10.8682	$10.87	$10.85	$10.90
Purchase #4	$168.73	4.459%	$176.2537	$176.25	$176.25	$176.30
Purchase #5	$135.41	5.815%	$143.2841	$143.28	$143.30	$143.30
Purchase #6	$50.47	13.234%	$57.1492	$57.15	$57.15	$57.10
Purchase #7	$223.87	8.731%	$243.4161	$243.42	$243.40	$243.40
7 purchase totals =	$820.18		$875.6420	$875.64	$875.60	$875.60