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	$141.91	5.200%	$149.2893	$149.29	$149.30	$149.30
Purchase #2	$165.90	3.777%	$172.166	$172.17	$172.15	$172.20
Purchase #3	$135.79	10.390%	$149.8986	$149.90	$149.90	$149.90
Purchase #4	$37.47	13.711%	$42.6075	$42.61	$42.60	$42.60
Purchase #5	$185.86	5.525%	$196.1288	$196.13	$196.15	$196.10
Purchase #6	$58.27	5.276%	$61.3443	$61.34	$61.35	$61.30
Purchase #7	$189.51	13.418%	$214.9385	$214.94	$214.95	$214.90
7 purchase totals =	$914.71		$986.3730	$986.38	$986.40	$986.30