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	$195.34	5.838%	$206.7439	$206.74	$206.75	$206.70
Purchase #2	$209.76	8.423%	$227.4281	$227.43	$227.45	$227.40
Purchase #3	$100.75	11.872%	$112.711	$112.71	$112.70	$112.70
Purchase #4	$222.33	12.192%	$249.4365	$249.44	$249.45	$249.40
Purchase #5	$228.89	5.701%	$241.939	$241.94	$241.95	$241.90
Purchase #6	$159.73	8.179%	$172.7943	$172.79	$172.80	$172.80
Purchase #7	$54.51	9.213%	$59.532	$59.53	$59.55	$59.50
7 purchase totals =	$1,171.31		$1,270.5848	$1,270.58	$1,270.65	$1,270.40