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	$105.97	6.809%	$113.1855	$113.19	$113.20	$113.20
Purchase #2	$120.64	8.689%	$131.1224	$131.12	$131.10	$131.10
Purchase #3	$84.52	4.428%	$88.2625	$88.26	$88.25	$88.30
Purchase #4	$220.96	8.648%	$240.0686	$240.07	$240.05	$240.10
Purchase #5	$200.43	10.761%	$221.9983	$222.00	$222.00	$222.00
Purchase #6	$88.50	12.828%	$99.8528	$99.85	$99.85	$99.90
Purchase #7	$100.51	12.209%	$112.7813	$112.78	$112.80	$112.80
7 purchase totals =	$921.53		$1,007.2714	$1,007.27	$1,007.25	$1,007.40