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	$228.53	11.759%	$255.4028	$255.40	$255.40	$255.40
Purchase #2	$93.83	12.315%	$105.3852	$105.39	$105.40	$105.40
Purchase #3	$215.41	3.712%	$223.406	$223.41	$223.40	$223.40
Purchase #4	$248.27	10.837%	$275.175	$275.18	$275.20	$275.20
Purchase #5	$6.38	6.711%	$6.8082	$6.81	$6.80	$6.80
Purchase #6	$177.90	13.107%	$201.2174	$201.22	$201.20	$201.20
Purchase #7	$106.45	5.296%	$112.0876	$112.09	$112.10	$112.10
7 purchase totals =	$1,076.77		$1,179.4822	$1,179.50	$1,179.50	$1,179.50