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	$207.85	3.440%	$215	$215.00	$215.00	$215.00
Purchase #2	$236.35	11.149%	$262.7007	$262.70	$262.70	$262.70
Purchase #3	$39.95	3.400%	$41.3083	$41.31	$41.30	$41.30
Purchase #4	$82.77	12.198%	$92.8663	$92.87	$92.85	$92.90
Purchase #5	$62.80	13.617%	$71.3515	$71.35	$71.35	$71.40
Purchase #6	$88.84	12.172%	$99.6536	$99.65	$99.65	$99.70
Purchase #7	$151.60	5.490%	$159.9228	$159.92	$159.90	$159.90
7 purchase totals =	$870.16		$942.8032	$942.80	$942.75	$942.90