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	$136.79	10.840%	$151.618	$151.62	$151.60	$151.60
Purchase #2	$41.47	9.579%	$45.4424	$45.44	$45.45	$45.40
Purchase #3	$105.80	10.296%	$116.6932	$116.69	$116.70	$116.70
Purchase #4	$57.40	3.780%	$59.5697	$59.57	$59.55	$59.60
Purchase #5	$75.88	11.244%	$84.4119	$84.41	$84.40	$84.40
Purchase #6	$55.97	4.575%	$58.5306	$58.53	$58.55	$58.50
Purchase #7	$200.40	6.232%	$212.8889	$212.89	$212.90	$212.90
7 purchase totals =	$673.71		$729.1547	$729.15	$729.15	$729.10