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	$152.36	13.265%	$172.5706	$172.57	$172.55	$172.60
Purchase #2	$130.72	7.675%	$140.7528	$140.75	$140.75	$140.80
Purchase #3	$185.69	7.519%	$199.652	$199.65	$199.65	$199.70
Purchase #4	$103.83	5.814%	$109.8667	$109.87	$109.85	$109.90
Purchase #5	$206.34	6.807%	$220.3856	$220.39	$220.40	$220.40
Purchase #6	$213.82	11.474%	$238.3537	$238.35	$238.35	$238.40
Purchase #7	$51.50	7.378%	$55.2997	$55.30	$55.30	$55.30
7 purchase totals =	$1,044.26		$1,136.8811	$1,136.88	$1,136.85	$1,137.10