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	$148.94	6.574%	$158.7313	$158.73	$158.75	$158.70
Purchase #2	$94.74	6.488%	$100.8867	$100.89	$100.90	$100.90
Purchase #3	$155.34	5.661%	$164.1338	$164.13	$164.15	$164.10
Purchase #4	$120.64	8.465%	$130.8522	$130.85	$130.85	$130.90
Purchase #5	$111.92	7.421%	$120.2256	$120.23	$120.25	$120.20
Purchase #6	$7.90	9.577%	$8.6566	$8.66	$8.65	$8.70
Purchase #7	$25.93	13.495%	$29.4293	$29.43	$29.45	$29.40
7 purchase totals =	$665.41		$712.9155	$712.92	$713.00	$712.90