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	$241.27	7.394%	$259.1095	$259.11	$259.10	$259.10
Purchase #2	$164.59	9.389%	$180.0434	$180.04	$180.05	$180.00
Purchase #3	$139.46	4.320%	$145.4847	$145.48	$145.50	$145.50
Purchase #4	$233.59	9.413%	$255.5778	$255.58	$255.60	$255.60
Purchase #5	$19.52	6.483%	$20.7855	$20.79	$20.80	$20.80
Purchase #6	$38.25	11.502%	$42.6495	$42.65	$42.65	$42.60
Purchase #7	$125.98	11.592%	$140.5836	$140.58	$140.60	$140.60
7 purchase totals =	$962.66		$1,044.2340	$1,044.23	$1,044.30	$1,044.20