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	$129.84	3.192%	$133.9845	$133.98	$134.00	$134.00
Purchase #2	$157.53	8.218%	$170.4758	$170.48	$170.50	$170.50
Purchase #3	$28.63	13.569%	$32.5148	$32.51	$32.50	$32.50
Purchase #4	$216.61	3.650%	$224.5163	$224.52	$224.50	$224.50
Purchase #5	$152.90	3.278%	$157.9121	$157.91	$157.90	$157.90
Purchase #6	$247.39	11.264%	$275.256	$275.26	$275.25	$275.30
Purchase #7	$19.99	11.427%	$22.2743	$22.27	$22.25	$22.30
7 purchase totals =	$952.89		$1,016.9338	$1,016.93	$1,016.90	$1,017.00