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	$60.60	7.422%	$65.0977	$65.10	$65.10	$65.10
Purchase #2	$91.54	9.583%	$100.3123	$100.31	$100.30	$100.30
Purchase #3	$185.90	10.629%	$205.6593	$205.66	$205.65	$205.70
Purchase #4	$218.57	8.588%	$237.3408	$237.34	$237.35	$237.30
Purchase #5	$94.25	12.121%	$105.674	$105.67	$105.65	$105.70
Purchase #6	$110.88	5.168%	$116.6103	$116.61	$116.60	$116.60
Purchase #7	$92.47	8.274%	$100.121	$100.12	$100.10	$100.10
7 purchase totals =	$854.21		$930.8154	$930.81	$930.75	$930.80