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	$246.55	7.700%	$265.5344	$265.53	$265.55	$265.50
Purchase #2	$168.36	7.243%	$180.5543	$180.55	$180.55	$180.60
Purchase #3	$39.60	7.449%	$42.5498	$42.55	$42.55	$42.50
Purchase #4	$185.46	9.725%	$203.496	$203.50	$203.50	$203.50
Purchase #5	$229.75	3.388%	$237.5339	$237.53	$237.55	$237.50
Purchase #6	$32.61	11.705%	$36.427	$36.43	$36.45	$36.40
Purchase #7	$152.26	13.549%	$172.8897	$172.89	$172.90	$172.90
7 purchase totals =	$1,054.59		$1,138.9851	$1,138.98	$1,139.05	$1,138.90