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	$150.83	5.114%	$158.5434	$158.54	$158.55	$158.50
Purchase #2	$64.35	5.379%	$67.8114	$67.81	$67.80	$67.80
Purchase #3	$17.59	3.198%	$18.1525	$18.15	$18.15	$18.20
Purchase #4	$202.98	6.222%	$215.6094	$215.61	$215.60	$215.60
Purchase #5	$195.71	13.764%	$222.6475	$222.65	$222.65	$222.60
Purchase #6	$84.40	13.505%	$95.7982	$95.80	$95.80	$95.80
Purchase #7	$221.48	7.221%	$237.4731	$237.47	$237.45	$237.50
7 purchase totals =	$937.34		$1,016.0355	$1,016.03	$1,016.00	$1,016.00