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	$225.57	13.328%	$255.634	$255.63	$255.65	$255.60
Purchase #2	$187.42	10.640%	$207.3615	$207.36	$207.35	$207.40
Purchase #3	$141.66	7.333%	$152.0479	$152.05	$152.05	$152.00
Purchase #4	$55.35	7.573%	$59.5417	$59.54	$59.55	$59.50
Purchase #5	$236.68	10.817%	$262.2817	$262.28	$262.30	$262.30
Purchase #6	$57.79	4.233%	$60.2363	$60.24	$60.25	$60.20
Purchase #7	$150.58	12.835%	$169.9069	$169.91	$169.90	$169.90
7 purchase totals =	$1,055.05		$1,167.0100	$1,167.01	$1,167.05	$1,166.90