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	$159.82	6.262%	$169.8279	$169.83	$169.85	$169.80
Purchase #2	$34.34	3.711%	$35.6144	$35.61	$35.60	$35.60
Purchase #3	$182.90	8.851%	$199.0885	$199.09	$199.10	$199.10
Purchase #4	$58.80	11.377%	$65.4897	$65.49	$65.50	$65.50
Purchase #5	$67.32	3.383%	$69.5974	$69.60	$69.60	$69.60
Purchase #6	$225.25	3.691%	$233.564	$233.56	$233.55	$233.60
Purchase #7	$77.70	7.771%	$83.7381	$83.74	$83.75	$83.70
7 purchase totals =	$806.13		$856.9200	$856.92	$856.95	$856.90