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	$145.78	11.440%	$162.4572	$162.46	$162.45	$162.50
Purchase #2	$69.64	12.385%	$78.2649	$78.26	$78.25	$78.30
Purchase #3	$157.84	10.215%	$173.9634	$173.96	$173.95	$174.00
Purchase #4	$232.96	10.296%	$256.9456	$256.95	$256.95	$256.90
Purchase #5	$50.68	7.473%	$54.4673	$54.47	$54.45	$54.50
Purchase #6	$157.47	9.761%	$172.8406	$172.84	$172.85	$172.80
Purchase #7	$134.67	9.431%	$147.3707	$147.37	$147.35	$147.40
7 purchase totals =	$949.04		$1,046.3097	$1,046.31	$1,046.25	$1,046.40