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	$140.80	13.803%	$160.2346	$160.23	$160.25	$160.20
Purchase #2	$70.37	11.540%	$78.4907	$78.49	$78.50	$78.50
Purchase #3	$30.57	5.864%	$32.3626	$32.36	$32.35	$32.40
Purchase #4	$138.99	11.569%	$155.0698	$155.07	$155.05	$155.10
Purchase #5	$149.26	4.562%	$156.0692	$156.07	$156.05	$156.10
Purchase #6	$103.73	8.539%	$112.5875	$112.59	$112.60	$112.60
Purchase #7	$47.46	8.113%	$51.3104	$51.31	$51.30	$51.30
7 purchase totals =	$681.18		$746.1248	$746.12	$746.10	$746.20