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	$110.76	11.693%	$123.7112	$123.71	$123.70	$123.70
Purchase #2	$64.95	11.658%	$72.5219	$72.52	$72.50	$72.50
Purchase #3	$67.88	11.356%	$75.5885	$75.59	$75.60	$75.60
Purchase #4	$61.57	7.689%	$66.3041	$66.30	$66.30	$66.30
Purchase #5	$175.89	5.398%	$185.3845	$185.38	$185.40	$185.40
Purchase #6	$39.57	5.549%	$41.7657	$41.77	$41.75	$41.80
Purchase #7	$221.74	11.854%	$248.0251	$248.03	$248.05	$248.00
7 purchase totals =	$742.36		$813.3010	$813.30	$813.30	$813.30