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	$245.39	11.605%	$273.8675	$273.87	$273.85	$273.90
Purchase #2	$30.29	4.683%	$31.7085	$31.71	$31.70	$31.70
Purchase #3	$78.57	13.504%	$89.1801	$89.18	$89.20	$89.20
Purchase #4	$184.91	7.550%	$198.8707	$198.87	$198.85	$198.90
Purchase #5	$10.95	8.654%	$11.8976	$11.90	$11.90	$11.90
Purchase #6	$82.98	13.779%	$94.4138	$94.41	$94.40	$94.40
Purchase #7	$119.71	5.223%	$125.9625	$125.96	$125.95	$126.00
7 purchase totals =	$752.80		$825.9007	$825.90	$825.85	$826.00