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	$162.92	3.672%	$168.9024	$168.90	$168.90	$168.90
Purchase #2	$92.55	8.463%	$100.3825	$100.38	$100.40	$100.40
Purchase #3	$153.43	8.510%	$166.4869	$166.49	$166.50	$166.50
Purchase #4	$81.31	6.861%	$86.8887	$86.89	$86.90	$86.90
Purchase #5	$33.48	6.828%	$35.766	$35.77	$35.75	$35.80
Purchase #6	$196.54	11.812%	$219.7553	$219.76	$219.75	$219.80
Purchase #7	$157.86	13.674%	$179.4458	$179.45	$179.45	$179.40
7 purchase totals =	$878.09		$957.6276	$957.64	$957.65	$957.70