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	$174.35	7.424%	$187.2937	$187.29	$187.30	$187.30
Purchase #2	$166.59	4.391%	$173.905	$173.91	$173.90	$173.90
Purchase #3	$223.93	3.555%	$231.8907	$231.89	$231.90	$231.90
Purchase #4	$227.51	9.230%	$248.5092	$248.51	$248.50	$248.50
Purchase #5	$152.69	3.445%	$157.9502	$157.95	$157.95	$158.00
Purchase #6	$132.96	9.368%	$145.4157	$145.42	$145.40	$145.40
Purchase #7	$35.63	13.850%	$40.5648	$40.56	$40.55	$40.60
7 purchase totals =	$1,113.66		$1,185.5293	$1,185.53	$1,185.50	$1,185.60