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	$203.80	10.753%	$225.7146	$225.71	$225.70	$225.70
Purchase #2	$242.98	8.244%	$263.0113	$263.01	$263.00	$263.00
Purchase #3	$234.89	11.794%	$262.5929	$262.59	$262.60	$262.60
Purchase #4	$103.55	12.595%	$116.5921	$116.59	$116.60	$116.60
Purchase #5	$125.63	4.843%	$131.7143	$131.71	$131.70	$131.70
Purchase #6	$110.79	11.741%	$123.7979	$123.80	$123.80	$123.80
Purchase #7	$231.53	8.192%	$250.4969	$250.50	$250.50	$250.50
7 purchase totals =	$1,253.17		$1,373.9200	$1,373.91	$1,373.90	$1,373.90