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	$203.47	6.530%	$216.7566	$216.76	$216.75	$216.80
Purchase #2	$53.56	13.256%	$60.6599	$60.66	$60.65	$60.70
Purchase #3	$82.86	6.352%	$88.1233	$88.12	$88.10	$88.10
Purchase #4	$55.97	6.195%	$59.4373	$59.44	$59.45	$59.40
Purchase #5	$244.65	4.841%	$256.4935	$256.49	$256.50	$256.50
Purchase #6	$237.75	5.340%	$250.4459	$250.45	$250.45	$250.40
Purchase #7	$7.33	8.256%	$7.9352	$7.94	$7.95	$7.90
7 purchase totals =	$885.59		$939.8517	$939.86	$939.85	$939.80