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	$135.75	3.745%	$140.8338	$140.83	$140.85	$140.80
Purchase #2	$98.57	5.858%	$104.3442	$104.34	$104.35	$104.30
Purchase #3	$173.74	7.405%	$186.6054	$186.61	$186.60	$186.60
Purchase #4	$146.91	4.313%	$153.2462	$153.25	$153.25	$153.20
Purchase #5	$248.76	9.504%	$272.4022	$272.40	$272.40	$272.40
Purchase #6	$141.76	6.708%	$151.2693	$151.27	$151.25	$151.30
Purchase #7	$50.96	8.545%	$55.3145	$55.31	$55.30	$55.30
7 purchase totals =	$996.45		$1,064.0156	$1,064.01	$1,064.00	$1,063.90