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	$199.91	6.154%	$212.2125	$212.21	$212.20	$212.20
Purchase #2	$222.86	11.781%	$249.1151	$249.12	$249.10	$249.10
Purchase #3	$246.85	3.430%	$255.317	$255.32	$255.30	$255.30
Purchase #4	$165.69	8.460%	$179.7074	$179.71	$179.70	$179.70
Purchase #5	$59.79	11.130%	$66.4446	$66.44	$66.45	$66.40
Purchase #6	$29.55	8.693%	$32.1188	$32.12	$32.10	$32.10
Purchase #7	$55.40	6.816%	$59.1761	$59.18	$59.20	$59.20
7 purchase totals =	$980.05		$1,054.0915	$1,054.10	$1,054.05	$1,054.00