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	$64.47	11.466%	$71.8621	$71.86	$71.85	$71.90
Purchase #2	$128.88	13.112%	$145.7787	$145.78	$145.80	$145.80
Purchase #3	$154.44	11.435%	$172.1002	$172.10	$172.10	$172.10
Purchase #4	$16.82	4.217%	$17.5293	$17.53	$17.55	$17.50
Purchase #5	$218.34	7.840%	$235.4579	$235.46	$235.45	$235.50
Purchase #6	$206.89	7.419%	$222.2392	$222.24	$222.25	$222.20
Purchase #7	$233.75	11.799%	$261.3302	$261.33	$261.35	$261.30
7 purchase totals =	$1,023.59		$1,126.2976	$1,126.30	$1,126.35	$1,126.30