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	$203.94	13.511%	$231.4943	$231.49	$231.50	$231.50
Purchase #2	$84.95	13.534%	$96.4471	$96.45	$96.45	$96.40
Purchase #3	$75.90	7.695%	$81.7405	$81.74	$81.75	$81.70
Purchase #4	$90.42	12.675%	$101.8807	$101.88	$101.90	$101.90
Purchase #5	$25.94	13.221%	$29.3695	$29.37	$29.35	$29.40
Purchase #6	$50.62	4.437%	$52.866	$52.87	$52.85	$52.90
Purchase #7	$153.83	4.315%	$160.4678	$160.47	$160.45	$160.50
7 purchase totals =	$685.60		$754.2659	$754.27	$754.25	$754.30