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	$210.63	10.196%	$232.1058	$232.11	$232.10	$232.10
Purchase #2	$176.34	10.355%	$194.6	$194.60	$194.60	$194.60
Purchase #3	$201.92	11.669%	$225.482	$225.48	$225.50	$225.50
Purchase #4	$231.67	9.621%	$253.959	$253.96	$253.95	$254.00
Purchase #5	$20.38	5.487%	$21.4983	$21.50	$21.50	$21.50
Purchase #6	$89.27	11.758%	$99.7664	$99.77	$99.75	$99.80
Purchase #7	$89.40	6.278%	$95.0125	$95.01	$95.00	$95.00
7 purchase totals =	$1,019.61		$1,122.4240	$1,122.43	$1,122.40	$1,122.50