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	$114.85	10.136%	$126.4912	$126.49	$126.50	$126.50
Purchase #2	$137.59	4.178%	$143.3385	$143.34	$143.35	$143.30
Purchase #3	$64.75	4.841%	$67.8845	$67.88	$67.90	$67.90
Purchase #4	$78.78	8.756%	$85.678	$85.68	$85.70	$85.70
Purchase #5	$92.69	8.199%	$100.2897	$100.29	$100.30	$100.30
Purchase #6	$99.92	12.566%	$112.4759	$112.48	$112.50	$112.50
Purchase #7	$168.30	4.506%	$175.8836	$175.88	$175.90	$175.90
7 purchase totals =	$756.88		$812.0414	$812.04	$812.15	$812.10