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	$44.45	5.574%	$46.9276	$46.93	$46.95	$46.90
Purchase #2	$249.36	11.267%	$277.4554	$277.46	$277.45	$277.50
Purchase #3	$106.73	12.200%	$119.7511	$119.75	$119.75	$119.80
Purchase #4	$85.74	5.561%	$90.508	$90.51	$90.50	$90.50
Purchase #5	$85.64	4.288%	$89.3122	$89.31	$89.30	$89.30
Purchase #6	$31.50	12.412%	$35.4098	$35.41	$35.40	$35.40
Purchase #7	$147.34	12.773%	$166.1597	$166.16	$166.15	$166.20
7 purchase totals =	$750.76		$825.5238	$825.53	$825.50	$825.60