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	$160.52	11.532%	$179.0312	$179.03	$179.05	$179.00
Purchase #2	$218.91	11.669%	$244.4546	$244.45	$244.45	$244.50
Purchase #3	$205.25	5.177%	$215.8758	$215.88	$215.90	$215.90
Purchase #4	$75.63	8.769%	$82.262	$82.26	$82.25	$82.30
Purchase #5	$149.70	10.650%	$165.6431	$165.64	$165.65	$165.60
Purchase #6	$40.39	11.536%	$45.0494	$45.05	$45.05	$45.00
Purchase #7	$184.95	5.741%	$195.568	$195.57	$195.55	$195.60
7 purchase totals =	$1,035.35		$1,127.8841	$1,127.88	$1,127.90	$1,127.90