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	$204.87	4.187%	$213.4479	$213.45	$213.45	$213.40
Purchase #2	$75.79	12.425%	$85.2069	$85.21	$85.20	$85.20
Purchase #3	$148.79	11.245%	$165.5214	$165.52	$165.50	$165.50
Purchase #4	$46.52	9.742%	$51.052	$51.05	$51.05	$51.10
Purchase #5	$143.37	9.826%	$157.4575	$157.46	$157.45	$157.50
Purchase #6	$163.55	5.116%	$171.9172	$171.92	$171.90	$171.90
Purchase #7	$109.82	12.362%	$123.3959	$123.40	$123.40	$123.40
7 purchase totals =	$892.71		$967.9988	$968.01	$967.95	$968.00