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	$50.42	6.672%	$53.784	$53.78	$53.80	$53.80
Purchase #2	$161.56	4.435%	$168.7252	$168.73	$168.75	$168.70
Purchase #3	$18.97	4.197%	$19.7662	$19.77	$19.75	$19.80
Purchase #4	$118.99	7.241%	$127.6061	$127.61	$127.60	$127.60
Purchase #5	$110.63	8.378%	$119.8986	$119.90	$119.90	$119.90
Purchase #6	$118.92	7.578%	$127.9318	$127.93	$127.95	$127.90
Purchase #7	$100.42	13.315%	$113.7909	$113.79	$113.80	$113.80
7 purchase totals =	$679.91		$731.5028	$731.51	$731.55	$731.50