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	$113.39	5.627%	$119.7705	$119.77	$119.75	$119.80
Purchase #2	$43.45	5.543%	$45.8584	$45.86	$45.85	$45.90
Purchase #3	$101.48	11.716%	$113.3694	$113.37	$113.35	$113.40
Purchase #4	$32.89	9.244%	$35.9304	$35.93	$35.95	$35.90
Purchase #5	$141.85	13.414%	$160.8778	$160.88	$160.90	$160.90
Purchase #6	$45.94	4.486%	$48.0009	$48.00	$48.00	$48.00
Purchase #7	$29.85	8.873%	$32.4986	$32.50	$32.50	$32.50
7 purchase totals =	$508.85		$556.3060	$556.31	$556.30	$556.40