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	$152.93	3.262%	$157.9186	$157.92	$157.90	$157.90
Purchase #2	$89.95	11.293%	$100.1081	$100.11	$100.10	$100.10
Purchase #3	$213.80	9.152%	$233.367	$233.37	$233.35	$233.40
Purchase #4	$152.53	11.658%	$170.3119	$170.31	$170.30	$170.30
Purchase #5	$223.87	3.832%	$232.4487	$232.45	$232.45	$232.40
Purchase #6	$72.81	7.188%	$78.0436	$78.04	$78.05	$78.00
Purchase #7	$245.93	10.810%	$272.515	$272.52	$272.50	$272.50
7 purchase totals =	$1,151.82		$1,244.7129	$1,244.72	$1,244.65	$1,244.60