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	$145.88	5.805%	$154.3483	$154.35	$154.35	$154.30
Purchase #2	$148.79	5.515%	$156.9958	$157.00	$157.00	$157.00
Purchase #3	$73.35	7.105%	$78.5615	$78.56	$78.55	$78.60
Purchase #4	$175.99	8.118%	$190.2769	$190.28	$190.30	$190.30
Purchase #5	$118.35	10.114%	$130.3199	$130.32	$130.30	$130.30
Purchase #6	$10.47	13.269%	$11.8593	$11.86	$11.85	$11.90
Purchase #7	$219.27	4.213%	$228.5078	$228.51	$228.50	$228.50
7 purchase totals =	$892.10		$950.8695	$950.88	$950.85	$950.90