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	$205.59	8.423%	$222.9068	$222.91	$222.90	$222.90
Purchase #2	$183.59	7.684%	$197.6971	$197.70	$197.70	$197.70
Purchase #3	$6.27	13.166%	$7.0955	$7.10	$7.10	$7.10
Purchase #4	$116.77	13.761%	$132.8387	$132.84	$132.85	$132.80
Purchase #5	$227.90	7.509%	$245.013	$245.01	$245.00	$245.00
Purchase #6	$146.26	12.733%	$164.8833	$164.88	$164.90	$164.90
Purchase #7	$196.81	12.456%	$221.3247	$221.32	$221.30	$221.30
7 purchase totals =	$1,083.19		$1,191.7591	$1,191.76	$1,191.75	$1,191.70