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	$145.73	4.804%	$152.7309	$152.73	$152.75	$152.70
Purchase #2	$25.45	8.584%	$27.6346	$27.63	$27.65	$27.60
Purchase #3	$34.72	3.120%	$35.8033	$35.80	$35.80	$35.80
Purchase #4	$234.70	13.167%	$265.6029	$265.60	$265.60	$265.60
Purchase #5	$175.40	8.755%	$190.7563	$190.76	$190.75	$190.80
Purchase #6	$92.84	9.380%	$101.5484	$101.55	$101.55	$101.50
Purchase #7	$45.98	4.191%	$47.907	$47.91	$47.90	$47.90
7 purchase totals =	$754.82		$821.9834	$821.98	$822.00	$821.90