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	$213.87	4.540%	$223.5797	$223.58	$223.60	$223.60
Purchase #2	$199.96	11.804%	$223.5633	$223.56	$223.55	$223.60
Purchase #3	$130.79	9.578%	$143.3171	$143.32	$143.30	$143.30
Purchase #4	$87.78	8.296%	$95.0622	$95.06	$95.05	$95.10
Purchase #5	$214.65	7.756%	$231.2983	$231.30	$231.30	$231.30
Purchase #6	$185.92	9.742%	$204.0323	$204.03	$204.05	$204.00
Purchase #7	$78.96	8.417%	$85.6061	$85.61	$85.60	$85.60
7 purchase totals =	$1,111.93		$1,206.4590	$1,206.46	$1,206.45	$1,206.50