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	$185.44	8.661%	$201.501	$201.50	$201.50	$201.50
Purchase #2	$149.75	11.445%	$166.8889	$166.89	$166.90	$166.90
Purchase #3	$10.51	3.171%	$10.8433	$10.84	$10.85	$10.80
Purchase #4	$114.50	7.454%	$123.0348	$123.03	$123.05	$123.00
Purchase #5	$175.82	11.569%	$196.1606	$196.16	$196.15	$196.20
Purchase #6	$224.55	7.851%	$242.1794	$242.18	$242.20	$242.20
Purchase #7	$109.71	13.294%	$124.2948	$124.29	$124.30	$124.30
7 purchase totals =	$970.28		$1,064.9028	$1,064.89	$1,064.95	$1,064.90