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	$217.46	7.386%	$233.5216	$233.52	$233.50	$233.50
Purchase #2	$156.61	6.696%	$167.0966	$167.10	$167.10	$167.10
Purchase #3	$129.71	10.354%	$143.1402	$143.14	$143.15	$143.10
Purchase #4	$136.61	10.846%	$151.4267	$151.43	$151.45	$151.40
Purchase #5	$222.58	6.188%	$236.3533	$236.35	$236.35	$236.40
Purchase #6	$216.78	11.187%	$241.0312	$241.03	$241.05	$241.00
Purchase #7	$149.79	12.698%	$168.8103	$168.81	$168.80	$168.80
7 purchase totals =	$1,229.54		$1,341.3799	$1,341.38	$1,341.40	$1,341.30