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	$105.32	4.344%	$109.8951	$109.90	$109.90	$109.90
Purchase #2	$62.43	8.773%	$67.907	$67.91	$67.90	$67.90
Purchase #3	$48.65	10.140%	$53.5831	$53.58	$53.60	$53.60
Purchase #4	$89.96	5.108%	$94.5552	$94.56	$94.55	$94.60
Purchase #5	$58.96	13.596%	$66.9762	$66.98	$67.00	$67.00
Purchase #6	$146.29	6.474%	$155.7608	$155.76	$155.75	$155.80
Purchase #7	$107.58	10.183%	$118.5349	$118.53	$118.55	$118.50
7 purchase totals =	$619.19		$667.2123	$667.22	$667.25	$667.30