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	$122.36	4.559%	$127.9384	$127.94	$127.95	$127.90
Purchase #2	$118.49	4.528%	$123.8552	$123.86	$123.85	$123.90
Purchase #3	$147.85	6.837%	$157.9585	$157.96	$157.95	$158.00
Purchase #4	$56.54	5.350%	$59.5649	$59.56	$59.55	$59.60
Purchase #5	$108.96	4.640%	$114.0157	$114.02	$114.00	$114.00
Purchase #6	$14.81	7.663%	$15.9449	$15.94	$15.95	$15.90
Purchase #7	$194.35	11.840%	$217.361	$217.36	$217.35	$217.40
7 purchase totals =	$763.36		$816.6386	$816.64	$816.60	$816.70