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	$110.60	11.548%	$123.3721	$123.37	$123.35	$123.40
Purchase #2	$177.90	6.317%	$189.1379	$189.14	$189.15	$189.10
Purchase #3	$161.78	12.663%	$182.2662	$182.27	$182.25	$182.30
Purchase #4	$122.83	13.333%	$139.2069	$139.21	$139.20	$139.20
Purchase #5	$39.94	8.264%	$43.2406	$43.24	$43.25	$43.20
Purchase #6	$203.88	10.538%	$225.3649	$225.36	$225.35	$225.40
Purchase #7	$124.80	13.870%	$142.1098	$142.11	$142.10	$142.10
7 purchase totals =	$941.73		$1,044.6984	$1,044.70	$1,044.65	$1,044.70