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	$200.59	6.204%	$213.0346	$213.03	$213.05	$213.00
Purchase #2	$77.65	7.753%	$83.6702	$83.67	$83.65	$83.70
Purchase #3	$207.53	11.698%	$231.8069	$231.81	$231.80	$231.80
Purchase #4	$166.86	7.790%	$179.8584	$179.86	$179.85	$179.90
Purchase #5	$116.95	12.115%	$131.1185	$131.12	$131.10	$131.10
Purchase #6	$64.61	12.117%	$72.4388	$72.44	$72.45	$72.40
Purchase #7	$167.28	3.111%	$172.4841	$172.48	$172.50	$172.50
7 purchase totals =	$1,001.47		$1,084.4115	$1,084.41	$1,084.40	$1,084.40