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	$149.78	8.439%	$162.4199	$162.42	$162.40	$162.40
Purchase #2	$238.51	7.704%	$256.8848	$256.88	$256.90	$256.90
Purchase #3	$131.84	11.658%	$147.2099	$147.21	$147.20	$147.20
Purchase #4	$237.65	8.388%	$257.5841	$257.58	$257.60	$257.60
Purchase #5	$182.88	5.764%	$193.4212	$193.42	$193.40	$193.40
Purchase #6	$192.86	10.161%	$212.4565	$212.46	$212.45	$212.50
Purchase #7	$182.60	7.647%	$196.5634	$196.56	$196.55	$196.60
7 purchase totals =	$1,316.12		$1,426.5398	$1,426.53	$1,426.50	$1,426.60