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	$133.91	6.333%	$142.3905	$142.39	$142.40	$142.40
Purchase #2	$146.92	13.334%	$166.5103	$166.51	$166.50	$166.50
Purchase #3	$137.50	11.117%	$152.7859	$152.79	$152.80	$152.80
Purchase #4	$45.76	6.322%	$48.6529	$48.65	$48.65	$48.70
Purchase #5	$100.57	3.288%	$103.8767	$103.88	$103.90	$103.90
Purchase #6	$110.71	3.775%	$114.8893	$114.89	$114.90	$114.90
Purchase #7	$246.38	8.109%	$266.359	$266.36	$266.35	$266.40
7 purchase totals =	$921.75		$995.4646	$995.47	$995.50	$995.60