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	$229.60	6.225%	$243.8926	$243.89	$243.90	$243.90
Purchase #2	$243.33	13.557%	$276.3182	$276.32	$276.30	$276.30
Purchase #3	$227.84	12.703%	$256.7825	$256.78	$256.80	$256.80
Purchase #4	$153.70	3.551%	$159.1579	$159.16	$159.15	$159.20
Purchase #5	$154.43	8.810%	$168.0353	$168.04	$168.05	$168.00
Purchase #6	$42.56	6.246%	$45.2183	$45.22	$45.20	$45.20
Purchase #7	$101.96	7.260%	$109.3623	$109.36	$109.35	$109.40
7 purchase totals =	$1,153.42		$1,258.7671	$1,258.77	$1,258.75	$1,258.80