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	$212.32	12.130%	$238.0744	$238.07	$238.05	$238.10
Purchase #2	$145.89	4.681%	$152.7191	$152.72	$152.70	$152.70
Purchase #3	$49.91	8.267%	$54.0361	$54.04	$54.05	$54.00
Purchase #4	$106.25	5.510%	$112.1044	$112.10	$112.10	$112.10
Purchase #5	$147.87	12.448%	$166.2769	$166.28	$166.30	$166.30
Purchase #6	$84.61	13.219%	$95.7946	$95.79	$95.80	$95.80
Purchase #7	$146.54	10.300%	$161.6336	$161.63	$161.65	$161.60
7 purchase totals =	$893.39		$980.6391	$980.63	$980.65	$980.60