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	$126.25	5.331%	$132.9804	$132.98	$133.00	$133.00
Purchase #2	$52.96	11.830%	$59.2252	$59.23	$59.25	$59.20
Purchase #3	$99.94	6.121%	$106.0573	$106.06	$106.05	$106.10
Purchase #4	$51.25	11.782%	$57.2883	$57.29	$57.30	$57.30
Purchase #5	$30.96	8.238%	$33.5105	$33.51	$33.50	$33.50
Purchase #6	$153.54	9.693%	$168.4226	$168.42	$168.40	$168.40
Purchase #7	$137.91	12.578%	$155.2563	$155.26	$155.25	$155.30
7 purchase totals =	$652.81		$712.7406	$712.75	$712.75	$712.80