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	$59.53	13.155%	$67.3612	$67.36	$67.35	$67.40
Purchase #2	$59.45	9.448%	$65.0668	$65.07	$65.05	$65.10
Purchase #3	$70.35	12.223%	$78.9489	$78.95	$78.95	$78.90
Purchase #4	$232.68	13.367%	$263.7823	$263.78	$263.80	$263.80
Purchase #5	$28.46	4.112%	$29.6303	$29.63	$29.65	$29.60
Purchase #6	$24.88	9.846%	$27.3297	$27.33	$27.35	$27.30
Purchase #7	$68.63	13.634%	$77.987	$77.99	$78.00	$78.00
7 purchase totals =	$543.98		$610.1062	$610.11	$610.15	$610.10