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	$151.73	6.419%	$161.4695	$161.47	$161.45	$161.50
Purchase #2	$122.69	8.278%	$132.8463	$132.85	$132.85	$132.80
Purchase #3	$221.83	7.205%	$237.8129	$237.81	$237.80	$237.80
Purchase #4	$70.42	11.374%	$78.4296	$78.43	$78.45	$78.40
Purchase #5	$191.65	3.661%	$198.6663	$198.67	$198.65	$198.70
Purchase #6	$142.95	13.872%	$162.78	$162.78	$162.80	$162.80
Purchase #7	$88.48	13.269%	$100.2204	$100.22	$100.20	$100.20
7 purchase totals =	$989.75		$1,072.2250	$1,072.23	$1,072.20	$1,072.20