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	$214.73	4.229%	$223.8109	$223.81	$223.80	$223.80
Purchase #2	$169.78	5.496%	$179.1111	$179.11	$179.10	$179.10
Purchase #3	$171.97	11.333%	$191.4594	$191.46	$191.45	$191.50
Purchase #4	$22.25	9.325%	$24.3248	$24.32	$24.30	$24.30
Purchase #5	$62.37	12.782%	$70.3421	$70.34	$70.35	$70.30
Purchase #6	$102.46	8.315%	$110.9795	$110.98	$111.00	$111.00
Purchase #7	$129.66	11.468%	$144.5294	$144.53	$144.55	$144.50
7 purchase totals =	$873.22		$944.5572	$944.55	$944.55	$944.50