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	$210.96	7.480%	$226.7398	$226.74	$226.75	$226.70
Purchase #2	$169.59	9.589%	$185.852	$185.85	$185.85	$185.90
Purchase #3	$135.72	4.843%	$142.2929	$142.29	$142.30	$142.30
Purchase #4	$30.73	10.266%	$33.8847	$33.88	$33.90	$33.90
Purchase #5	$37.47	8.600%	$40.6924	$40.69	$40.70	$40.70
Purchase #6	$86.35	4.426%	$90.1719	$90.17	$90.15	$90.20
Purchase #7	$214.90	7.196%	$230.3642	$230.36	$230.35	$230.40
7 purchase totals =	$885.72		$949.9979	$949.98	$950.00	$950.10