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	$112.43	13.306%	$127.3899	$127.39	$127.40	$127.40
Purchase #2	$89.61	3.447%	$92.6989	$92.70	$92.70	$92.70
Purchase #3	$214.65	13.218%	$243.0224	$243.02	$243.00	$243.00
Purchase #4	$195.49	13.469%	$221.8205	$221.82	$221.80	$221.80
Purchase #5	$209.75	7.509%	$225.5001	$225.50	$225.50	$225.50
Purchase #6	$238.78	10.284%	$263.3361	$263.34	$263.35	$263.30
Purchase #7	$180.69	5.483%	$190.5972	$190.60	$190.60	$190.60
7 purchase totals =	$1,241.40		$1,364.3651	$1,364.37	$1,364.35	$1,364.30