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	$242.35	9.561%	$265.5211	$265.52	$265.50	$265.50
Purchase #2	$134.89	6.331%	$143.4299	$143.43	$143.45	$143.40
Purchase #3	$146.25	11.298%	$162.7733	$162.77	$162.75	$162.80
Purchase #4	$56.81	5.161%	$59.742	$59.74	$59.75	$59.70
Purchase #5	$216.66	5.806%	$229.2393	$229.24	$229.25	$229.20
Purchase #6	$166.98	6.870%	$178.4515	$178.45	$178.45	$178.50
Purchase #7	$169.69	11.368%	$188.9804	$188.98	$189.00	$189.00
7 purchase totals =	$1,133.63		$1,228.1375	$1,228.13	$1,228.15	$1,228.10