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	$57.42	5.799%	$60.7498	$60.75	$60.75	$60.70
Purchase #2	$177.27	6.635%	$189.0319	$189.03	$189.05	$189.00
Purchase #3	$124.89	5.509%	$131.7702	$131.77	$131.75	$131.80
Purchase #4	$243.62	12.731%	$274.6353	$274.64	$274.65	$274.60
Purchase #5	$99.95	4.843%	$104.7906	$104.79	$104.80	$104.80
Purchase #6	$242.69	5.412%	$255.8244	$255.82	$255.80	$255.80
Purchase #7	$177.72	11.725%	$198.5577	$198.56	$198.55	$198.60
7 purchase totals =	$1,123.56		$1,215.3599	$1,215.36	$1,215.35	$1,215.30