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	$22.94	4.450%	$23.9608	$23.96	$23.95	$24.00
Purchase #2	$133.82	8.452%	$145.1305	$145.13	$145.15	$145.10
Purchase #3	$141.75	7.508%	$152.3926	$152.39	$152.40	$152.40
Purchase #4	$237.66	7.756%	$256.0929	$256.09	$256.10	$256.10
Purchase #5	$86.68	4.804%	$90.8441	$90.84	$90.85	$90.80
Purchase #6	$233.48	12.499%	$262.6627	$262.66	$262.65	$262.70
Purchase #7	$151.53	9.391%	$165.7602	$165.76	$165.75	$165.80
7 purchase totals =	$1,007.86		$1,096.8438	$1,096.83	$1,096.85	$1,096.90