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	$165.63	7.171%	$177.5073	$177.51	$177.50	$177.50
Purchase #2	$44.98	12.784%	$50.7302	$50.73	$50.75	$50.70
Purchase #3	$96.32	4.345%	$100.5051	$100.51	$100.50	$100.50
Purchase #4	$177.48	8.369%	$192.3333	$192.33	$192.35	$192.30
Purchase #5	$156.35	13.721%	$177.8028	$177.80	$177.80	$177.80
Purchase #6	$151.40	13.802%	$172.2962	$172.30	$172.30	$172.30
Purchase #7	$124.98	5.271%	$131.5677	$131.57	$131.55	$131.60
7 purchase totals =	$917.14		$1,002.7426	$1,002.75	$1,002.75	$1,002.70