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	$186.84	11.388%	$208.1173	$208.12	$208.10	$208.10
Purchase #2	$55.54	11.339%	$61.8377	$61.84	$61.85	$61.80
Purchase #3	$167.43	7.369%	$179.7679	$179.77	$179.75	$179.80
Purchase #4	$161.43	5.861%	$170.8914	$170.89	$170.90	$170.90
Purchase #5	$209.29	13.213%	$236.9435	$236.94	$236.95	$236.90
Purchase #6	$223.42	12.231%	$250.7465	$250.75	$250.75	$250.70
Purchase #7	$80.59	3.412%	$83.3397	$83.34	$83.35	$83.30
7 purchase totals =	$1,084.54		$1,191.6440	$1,191.65	$1,191.65	$1,191.50