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	$152.96	12.857%	$172.6261	$172.63	$172.65	$172.60
Purchase #2	$229.89	11.653%	$256.6791	$256.68	$256.70	$256.70
Purchase #3	$152.71	13.702%	$173.6343	$173.63	$173.65	$173.60
Purchase #4	$164.67	9.403%	$180.1539	$180.15	$180.15	$180.20
Purchase #5	$25.46	4.244%	$26.5405	$26.54	$26.55	$26.50
Purchase #6	$169.62	9.269%	$185.3421	$185.34	$185.35	$185.30
Purchase #7	$143.69	12.753%	$162.0148	$162.01	$162.00	$162.00
7 purchase totals =	$1,039.00		$1,156.9908	$1,156.98	$1,157.05	$1,156.90