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	$69.70	4.127%	$72.5765	$72.58	$72.60	$72.60
Purchase #2	$40.50	3.364%	$41.8624	$41.86	$41.85	$41.90
Purchase #3	$36.78	7.416%	$39.5076	$39.51	$39.50	$39.50
Purchase #4	$144.35	10.156%	$159.0102	$159.01	$159.00	$159.00
Purchase #5	$33.30	7.259%	$35.7172	$35.72	$35.70	$35.70
Purchase #6	$125.73	9.171%	$137.2607	$137.26	$137.25	$137.30
Purchase #7	$68.34	13.506%	$77.57	$77.57	$77.55	$77.60
7 purchase totals =	$518.70		$563.5046	$563.51	$563.45	$563.60