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	$134.66	4.606%	$140.8624	$140.86	$140.85	$140.90
Purchase #2	$88.34	5.133%	$92.8745	$92.87	$92.85	$92.90
Purchase #3	$226.56	12.572%	$255.0431	$255.04	$255.05	$255.00
Purchase #4	$108.47	8.261%	$117.4307	$117.43	$117.45	$117.40
Purchase #5	$48.37	11.185%	$53.7802	$53.78	$53.80	$53.80
Purchase #6	$207.63	10.516%	$229.4644	$229.46	$229.45	$229.50
Purchase #7	$203.34	13.518%	$230.8275	$230.83	$230.85	$230.80
7 purchase totals =	$1,017.37		$1,120.2828	$1,120.27	$1,120.30	$1,120.30