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	$191.95	12.769%	$216.4601	$216.46	$216.45	$216.50
Purchase #2	$59.28	9.387%	$64.8446	$64.84	$64.85	$64.80
Purchase #3	$33.55	11.743%	$37.4898	$37.49	$37.50	$37.50
Purchase #4	$216.85	11.114%	$240.9507	$240.95	$240.95	$241.00
Purchase #5	$209.89	7.600%	$225.8416	$225.84	$225.85	$225.80
Purchase #6	$22.75	13.796%	$25.8886	$25.89	$25.90	$25.90
Purchase #7	$222.38	6.131%	$236.0141	$236.01	$236.00	$236.00
7 purchase totals =	$956.65		$1,047.4895	$1,047.48	$1,047.50	$1,047.50