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	$33.25	13.456%	$37.7241	$37.72	$37.70	$37.70
Purchase #2	$92.55	13.447%	$104.9952	$105.00	$105.00	$105.00
Purchase #3	$151.42	10.110%	$166.7286	$166.73	$166.75	$166.70
Purchase #4	$119.56	4.400%	$124.8206	$124.82	$124.80	$124.80
Purchase #5	$211.93	5.730%	$224.0736	$224.07	$224.05	$224.10
Purchase #6	$215.43	13.730%	$245.0085	$245.01	$245.00	$245.00
Purchase #7	$133.87	6.163%	$142.1204	$142.12	$142.10	$142.10
7 purchase totals =	$958.01		$1,045.4710	$1,045.47	$1,045.40	$1,045.40