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	$177.89	9.342%	$194.5085	$194.51	$194.50	$194.50
Purchase #2	$144.56	4.828%	$151.5394	$151.54	$151.55	$151.50
Purchase #3	$140.96	4.135%	$146.7887	$146.79	$146.80	$146.80
Purchase #4	$96.34	9.102%	$105.1089	$105.11	$105.10	$105.10
Purchase #5	$61.64	9.154%	$67.2825	$67.28	$67.30	$67.30
Purchase #6	$23.79	7.776%	$25.6399	$25.64	$25.65	$25.60
Purchase #7	$166.43	9.609%	$182.4223	$182.42	$182.40	$182.40
7 purchase totals =	$811.61		$873.2902	$873.29	$873.30	$873.20