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	$140.52	12.705%	$158.3731	$158.37	$158.35	$158.40
Purchase #2	$45.43	13.443%	$51.5372	$51.54	$51.55	$51.50
Purchase #3	$215.71	13.117%	$244.0047	$244.00	$244.00	$244.00
Purchase #4	$49.56	3.250%	$51.1707	$51.17	$51.15	$51.20
Purchase #5	$243.48	11.537%	$271.5703	$271.57	$271.55	$271.60
Purchase #6	$202.87	11.139%	$225.4677	$225.47	$225.45	$225.50
Purchase #7	$160.37	12.413%	$180.2767	$180.28	$180.30	$180.30
7 purchase totals =	$1,057.94		$1,182.4004	$1,182.40	$1,182.35	$1,182.50