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	$180.38	5.261%	$189.8698	$189.87	$189.85	$189.90
Purchase #2	$149.31	12.753%	$168.3515	$168.35	$168.35	$168.40
Purchase #3	$246.73	8.308%	$267.2283	$267.23	$267.25	$267.20
Purchase #4	$177.78	5.497%	$187.5526	$187.55	$187.55	$187.60
Purchase #5	$160.28	7.731%	$172.6712	$172.67	$172.65	$172.70
Purchase #6	$46.39	6.369%	$49.3446	$49.34	$49.35	$49.30
Purchase #7	$162.89	11.282%	$181.2672	$181.27	$181.25	$181.30
7 purchase totals =	$1,123.76		$1,216.2852	$1,216.28	$1,216.25	$1,216.40