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	$144.84	4.865%	$151.8865	$151.89	$151.90	$151.90
Purchase #2	$49.50	5.821%	$52.3814	$52.38	$52.40	$52.40
Purchase #3	$16.30	4.196%	$16.9839	$16.98	$17.00	$17.00
Purchase #4	$126.62	11.382%	$141.0319	$141.03	$141.05	$141.00
Purchase #5	$119.61	3.298%	$123.5547	$123.55	$123.55	$123.60
Purchase #6	$195.64	13.679%	$222.4016	$222.40	$222.40	$222.40
Purchase #7	$198.99	4.628%	$208.1993	$208.20	$208.20	$208.20
7 purchase totals =	$851.50		$916.4393	$916.43	$916.50	$916.50