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	$124.43	7.404%	$133.6428	$133.64	$133.65	$133.60
Purchase #2	$111.54	4.577%	$116.6452	$116.65	$116.65	$116.60
Purchase #3	$69.36	13.230%	$78.5363	$78.54	$78.55	$78.50
Purchase #4	$13.84	13.722%	$15.7391	$15.74	$15.75	$15.70
Purchase #5	$175.71	4.813%	$184.1669	$184.17	$184.15	$184.20
Purchase #6	$99.29	6.694%	$105.9365	$105.94	$105.95	$105.90
Purchase #7	$213.47	9.818%	$234.4285	$234.43	$234.45	$234.40
7 purchase totals =	$807.64		$869.0953	$869.11	$869.15	$868.90