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	$182.45	13.169%	$206.4768	$206.48	$206.50	$206.50
Purchase #2	$64.56	10.505%	$71.342	$71.34	$71.35	$71.30
Purchase #3	$103.42	3.360%	$106.8949	$106.89	$106.90	$106.90
Purchase #4	$237.57	8.398%	$257.5211	$257.52	$257.50	$257.50
Purchase #5	$72.78	6.426%	$77.4568	$77.46	$77.45	$77.50
Purchase #6	$141.85	11.751%	$158.5188	$158.52	$158.50	$158.50
Purchase #7	$67.72	5.133%	$71.1961	$71.20	$71.20	$71.20
7 purchase totals =	$870.35		$949.4065	$949.41	$949.40	$949.40