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	$29.94	7.496%	$32.1843	$32.18	$32.20	$32.20
Purchase #2	$18.65	8.139%	$20.1679	$20.17	$20.15	$20.20
Purchase #3	$133.89	11.110%	$148.7652	$148.77	$148.75	$148.80
Purchase #4	$179.95	11.428%	$200.5147	$200.51	$200.50	$200.50
Purchase #5	$90.37	13.690%	$102.7417	$102.74	$102.75	$102.70
Purchase #6	$167.44	9.581%	$183.4824	$183.48	$183.50	$183.50
Purchase #7	$36.82	11.690%	$41.1243	$41.12	$41.10	$41.10
7 purchase totals =	$657.06		$728.9805	$728.97	$728.95	$729.00