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	$148.84	7.515%	$160.0253	$160.03	$160.05	$160.00
Purchase #2	$138.62	3.700%	$143.7489	$143.75	$143.75	$143.70
Purchase #3	$167.74	13.563%	$190.4906	$190.49	$190.50	$190.50
Purchase #4	$105.85	11.650%	$118.1815	$118.18	$118.20	$118.20
Purchase #5	$92.46	3.115%	$95.3401	$95.34	$95.35	$95.30
Purchase #6	$182.70	4.617%	$191.1353	$191.14	$191.15	$191.10
Purchase #7	$169.48	13.782%	$192.8377	$192.84	$192.85	$192.80
7 purchase totals =	$1,005.69		$1,091.7594	$1,091.77	$1,091.85	$1,091.60