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	$91.56	4.384%	$95.574	$95.57	$95.55	$95.60
Purchase #2	$92.46	10.450%	$102.1221	$102.12	$102.10	$102.10
Purchase #3	$6.89	13.362%	$7.8106	$7.81	$7.80	$7.80
Purchase #4	$248.59	10.449%	$274.5652	$274.57	$274.55	$274.60
Purchase #5	$225.90	5.596%	$238.5414	$238.54	$238.55	$238.50
Purchase #6	$116.94	5.239%	$123.0665	$123.07	$123.05	$123.10
Purchase #7	$72.33	7.473%	$77.7352	$77.74	$77.75	$77.70
7 purchase totals =	$854.67		$919.4150	$919.42	$919.35	$919.40