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	$73.54	12.260%	$82.556	$82.56	$82.55	$82.60
Purchase #2	$132.89	10.461%	$146.7916	$146.79	$146.80	$146.80
Purchase #3	$118.37	4.412%	$123.5925	$123.59	$123.60	$123.60
Purchase #4	$250.64	6.105%	$265.9416	$265.94	$265.95	$265.90
Purchase #5	$153.73	9.799%	$168.794	$168.79	$168.80	$168.80
Purchase #6	$143.85	5.340%	$151.5316	$151.53	$151.55	$151.50
Purchase #7	$87.33	7.263%	$93.6728	$93.67	$93.65	$93.70
7 purchase totals =	$960.35		$1,032.8801	$1,032.87	$1,032.90	$1,032.90