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	$132.45	13.340%	$150.1188	$150.12	$150.10	$150.10
Purchase #2	$85.52	6.858%	$91.385	$91.39	$91.40	$91.40
Purchase #3	$176.42	6.142%	$187.2557	$187.26	$187.25	$187.30
Purchase #4	$204.54	3.225%	$211.1364	$211.14	$211.15	$211.10
Purchase #5	$208.73	3.538%	$216.1149	$216.11	$216.10	$216.10
Purchase #6	$10.51	6.810%	$11.2257	$11.23	$11.25	$11.20
Purchase #7	$178.37	12.619%	$200.8785	$200.88	$200.90	$200.90
7 purchase totals =	$996.54		$1,068.1150	$1,068.13	$1,068.15	$1,068.10