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	$32.30	11.167%	$35.9069	$35.91	$35.90	$35.90
Purchase #2	$42.46	3.582%	$43.9809	$43.98	$44.00	$44.00
Purchase #3	$240.70	6.735%	$256.9111	$256.91	$256.90	$256.90
Purchase #4	$13.31	8.188%	$14.3998	$14.40	$14.40	$14.40
Purchase #5	$80.35	6.552%	$85.6145	$85.61	$85.60	$85.60
Purchase #6	$46.83	8.611%	$50.8625	$50.86	$50.85	$50.90
Purchase #7	$214.77	8.777%	$233.6204	$233.62	$233.60	$233.60
7 purchase totals =	$670.72		$721.2961	$721.29	$721.25	$721.30