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	$181.86	9.347%	$198.8585	$198.86	$198.85	$198.90
Purchase #2	$95.39	4.311%	$99.5023	$99.50	$99.50	$99.50
Purchase #3	$84.47	4.834%	$88.5533	$88.55	$88.55	$88.60
Purchase #4	$144.50	4.423%	$150.8912	$150.89	$150.90	$150.90
Purchase #5	$156.27	8.188%	$169.0654	$169.07	$169.05	$169.10
Purchase #6	$49.78	3.839%	$51.6911	$51.69	$51.70	$51.70
Purchase #7	$123.31	9.287%	$134.7618	$134.76	$134.75	$134.80
7 purchase totals =	$835.58		$893.3236	$893.32	$893.30	$893.50