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	$156.39	7.487%	$168.0989	$168.10	$168.10	$168.10
Purchase #2	$82.70	9.395%	$90.4697	$90.47	$90.45	$90.50
Purchase #3	$36.42	8.533%	$39.5277	$39.53	$39.55	$39.50
Purchase #4	$8.73	13.358%	$9.8962	$9.90	$9.90	$9.90
Purchase #5	$237.55	11.110%	$263.9418	$263.94	$263.95	$263.90
Purchase #6	$215.63	12.830%	$243.2953	$243.30	$243.30	$243.30
Purchase #7	$206.83	13.297%	$234.3322	$234.33	$234.35	$234.30
7 purchase totals =	$944.25		$1,049.5618	$1,049.57	$1,049.60	$1,049.50