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	$53.75	5.102%	$56.4923	$56.49	$56.50	$56.50
Purchase #2	$9.47	8.470%	$10.2721	$10.27	$10.25	$10.30
Purchase #3	$123.33	6.266%	$131.0579	$131.06	$131.05	$131.10
Purchase #4	$139.56	4.260%	$145.5053	$145.51	$145.50	$145.50
Purchase #5	$124.60	13.180%	$141.0223	$141.02	$141.00	$141.00
Purchase #6	$144.26	5.222%	$151.7933	$151.79	$151.80	$151.80
Purchase #7	$110.81	5.837%	$117.278	$117.28	$117.30	$117.30
7 purchase totals =	$705.78		$753.4212	$753.42	$753.40	$753.50