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	$103.34	8.793%	$112.4267	$112.43	$112.45	$112.40
Purchase #2	$213.29	13.619%	$242.338	$242.34	$242.35	$242.30
Purchase #3	$110.94	11.319%	$123.4973	$123.50	$123.50	$123.50
Purchase #4	$97.29	8.835%	$105.8856	$105.89	$105.90	$105.90
Purchase #5	$133.31	7.590%	$143.4282	$143.43	$143.45	$143.40
Purchase #6	$177.59	12.483%	$199.7586	$199.76	$199.75	$199.80
Purchase #7	$232.35	6.324%	$247.0438	$247.04	$247.05	$247.00
7 purchase totals =	$1,068.11		$1,174.3782	$1,174.39	$1,174.45	$1,174.30