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	$147.77	5.674%	$156.1545	$156.15	$156.15	$156.20
Purchase #2	$82.83	6.290%	$88.04	$88.04	$88.05	$88.00
Purchase #3	$190.56	9.380%	$208.4345	$208.43	$208.45	$208.40
Purchase #4	$144.57	4.540%	$151.1335	$151.13	$151.15	$151.10
Purchase #5	$73.46	11.486%	$81.8976	$81.90	$81.90	$81.90
Purchase #6	$126.89	9.212%	$138.5791	$138.58	$138.60	$138.60
Purchase #7	$176.52	12.672%	$198.8886	$198.89	$198.90	$198.90
7 purchase totals =	$942.60		$1,023.1278	$1,023.12	$1,023.20	$1,023.10