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	$152.69	8.816%	$166.1512	$166.15	$166.15	$166.20
Purchase #2	$88.54	4.237%	$92.2914	$92.29	$92.30	$92.30
Purchase #3	$40.26	5.196%	$42.3519	$42.35	$42.35	$42.40
Purchase #4	$7.25	4.338%	$7.5645	$7.56	$7.55	$7.60
Purchase #5	$42.40	9.450%	$46.4068	$46.41	$46.40	$46.40
Purchase #6	$180.53	13.333%	$204.6001	$204.60	$204.60	$204.60
Purchase #7	$107.96	9.603%	$118.3274	$118.33	$118.35	$118.30
7 purchase totals =	$619.63		$677.6933	$677.69	$677.70	$677.80