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	$145.91	3.254%	$150.6579	$150.66	$150.65	$150.70
Purchase #2	$220.65	12.146%	$247.4501	$247.45	$247.45	$247.50
Purchase #3	$62.55	4.874%	$65.5987	$65.60	$65.60	$65.60
Purchase #4	$31.90	10.700%	$35.3133	$35.31	$35.30	$35.30
Purchase #5	$24.76	12.433%	$27.8384	$27.84	$27.85	$27.80
Purchase #6	$156.29	8.489%	$169.5575	$169.56	$169.55	$169.60
Purchase #7	$223.31	12.628%	$251.5096	$251.51	$251.50	$251.50
7 purchase totals =	$865.37		$947.9255	$947.93	$947.90	$948.00