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	$160.54	11.579%	$179.1289	$179.13	$179.15	$179.10
Purchase #2	$13.94	3.251%	$14.3932	$14.39	$14.40	$14.40
Purchase #3	$56.90	4.233%	$59.3086	$59.31	$59.30	$59.30
Purchase #4	$245.50	4.124%	$255.6244	$255.62	$255.60	$255.60
Purchase #5	$70.92	8.219%	$76.7489	$76.75	$76.75	$76.70
Purchase #6	$141.47	13.794%	$160.9844	$160.98	$161.00	$161.00
Purchase #7	$154.54	3.473%	$159.9072	$159.91	$159.90	$159.90
7 purchase totals =	$843.81		$906.0956	$906.09	$906.10	$906.00