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	$90.96	6.199%	$96.5986	$96.60	$96.60	$96.60
Purchase #2	$204.29	8.387%	$221.4238	$221.42	$221.40	$221.40
Purchase #3	$59.92	13.132%	$67.7887	$67.79	$67.80	$67.80
Purchase #4	$35.81	4.742%	$37.5081	$37.51	$37.50	$37.50
Purchase #5	$88.74	5.549%	$93.6642	$93.66	$93.65	$93.70
Purchase #6	$86.35	10.742%	$95.6257	$95.63	$95.65	$95.60
Purchase #7	$39.30	3.132%	$40.5309	$40.53	$40.55	$40.50
7 purchase totals =	$605.37		$653.1400	$653.14	$653.15	$653.10