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	$118.26	10.317%	$130.4609	$130.46	$130.45	$130.50
Purchase #2	$154.99	7.341%	$166.3678	$166.37	$166.35	$166.40
Purchase #3	$213.51	13.821%	$243.0192	$243.02	$243.00	$243.00
Purchase #4	$216.82	9.359%	$237.1122	$237.11	$237.10	$237.10
Purchase #5	$242.92	4.312%	$253.3947	$253.39	$253.40	$253.40
Purchase #6	$6.89	8.445%	$7.4719	$7.47	$7.45	$7.50
Purchase #7	$78.88	9.222%	$86.1543	$86.15	$86.15	$86.20
7 purchase totals =	$1,032.27		$1,123.9810	$1,123.97	$1,123.90	$1,124.10