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	$65.57	10.593%	$72.5158	$72.52	$72.50	$72.50
Purchase #2	$16.73	6.621%	$17.8377	$17.84	$17.85	$17.80
Purchase #3	$20.66	6.560%	$22.0153	$22.02	$22.00	$22.00
Purchase #4	$128.92	10.838%	$142.8923	$142.89	$142.90	$142.90
Purchase #5	$71.52	11.869%	$80.0087	$80.01	$80.00	$80.00
Purchase #6	$20.67	5.155%	$21.7355	$21.74	$21.75	$21.70
Purchase #7	$41.27	9.362%	$45.1337	$45.13	$45.15	$45.10
7 purchase totals =	$365.34		$402.1390	$402.15	$402.15	$402.00