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	$46.41	13.289%	$52.5774	$52.58	$52.60	$52.60
Purchase #2	$80.26	13.192%	$90.8479	$90.85	$90.85	$90.80
Purchase #3	$225.54	5.381%	$237.6763	$237.68	$237.70	$237.70
Purchase #4	$202.43	6.287%	$215.1568	$215.16	$215.15	$215.20
Purchase #5	$86.77	9.689%	$95.1771	$95.18	$95.20	$95.20
Purchase #6	$37.68	3.538%	$39.0131	$39.01	$39.00	$39.00
Purchase #7	$67.71	6.251%	$71.9426	$71.94	$71.95	$71.90
7 purchase totals =	$746.80		$802.3912	$802.40	$802.45	$802.40