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	$199.79	11.171%	$222.1085	$222.11	$222.10	$222.10
Purchase #2	$146.42	7.755%	$157.7749	$157.77	$157.75	$157.80
Purchase #3	$146.27	12.623%	$164.7337	$164.73	$164.75	$164.70
Purchase #4	$75.59	9.162%	$82.5156	$82.52	$82.50	$82.50
Purchase #5	$163.82	3.165%	$169.0049	$169.00	$169.00	$169.00
Purchase #6	$143.50	5.805%	$151.8302	$151.83	$151.85	$151.80
Purchase #7	$182.78	11.269%	$203.3775	$203.38	$203.40	$203.40
7 purchase totals =	$1,058.17		$1,151.3453	$1,151.34	$1,151.35	$1,151.30