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	$159.39	7.572%	$171.459	$171.46	$171.45	$171.50
Purchase #2	$154.47	7.360%	$165.839	$165.84	$165.85	$165.80
Purchase #3	$22.50	8.558%	$24.4256	$24.43	$24.45	$24.40
Purchase #4	$63.26	6.660%	$67.4731	$67.47	$67.45	$67.50
Purchase #5	$186.84	13.550%	$212.1568	$212.16	$212.15	$212.20
Purchase #6	$60.51	8.441%	$65.6176	$65.62	$65.60	$65.60
Purchase #7	$176.27	5.205%	$185.4449	$185.44	$185.45	$185.40
7 purchase totals =	$823.24		$892.4160	$892.42	$892.40	$892.40