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	$212.32	13.563%	$241.117	$241.12	$241.10	$241.10
Purchase #2	$55.53	4.262%	$57.8967	$57.90	$57.90	$57.90
Purchase #3	$14.81	7.136%	$15.8668	$15.87	$15.85	$15.90
Purchase #4	$17.37	9.515%	$19.0228	$19.02	$19.00	$19.00
Purchase #5	$42.89	8.436%	$46.5082	$46.51	$46.50	$46.50
Purchase #6	$179.31	10.865%	$198.792	$198.79	$198.80	$198.80
Purchase #7	$64.39	4.454%	$67.2579	$67.26	$67.25	$67.30
7 purchase totals =	$586.62		$646.4614	$646.47	$646.40	$646.50