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	$150.74	7.805%	$162.5053	$162.51	$162.50	$162.50
Purchase #2	$45.89	10.760%	$50.8278	$50.83	$50.85	$50.80
Purchase #3	$107.94	3.806%	$112.0482	$112.05	$112.05	$112.00
Purchase #4	$103.30	8.547%	$112.1291	$112.13	$112.15	$112.10
Purchase #5	$142.85	11.559%	$159.362	$159.36	$159.35	$159.40
Purchase #6	$194.96	12.287%	$218.9147	$218.91	$218.90	$218.90
Purchase #7	$123.33	10.114%	$135.8036	$135.80	$135.80	$135.80
7 purchase totals =	$869.01		$951.5907	$951.59	$951.60	$951.50