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	$40.70	11.782%	$45.4953	$45.50	$45.50	$45.50
Purchase #2	$224.49	8.679%	$243.9735	$243.97	$243.95	$244.00
Purchase #3	$94.47	11.551%	$105.3822	$105.38	$105.40	$105.40
Purchase #4	$167.95	10.293%	$185.2371	$185.24	$185.25	$185.20
Purchase #5	$173.87	3.138%	$179.326	$179.33	$179.35	$179.30
Purchase #6	$74.96	12.806%	$84.5594	$84.56	$84.55	$84.60
Purchase #7	$148.76	4.525%	$155.4914	$155.49	$155.50	$155.50
7 purchase totals =	$925.20		$999.4649	$999.47	$999.50	$999.50