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	$56.47	9.473%	$61.8194	$61.82	$61.80	$61.80
Purchase #2	$26.45	13.178%	$29.9356	$29.94	$29.95	$29.90
Purchase #3	$193.65	10.251%	$213.5011	$213.50	$213.50	$213.50
Purchase #4	$197.69	10.599%	$218.6432	$218.64	$218.65	$218.60
Purchase #5	$205.79	6.540%	$219.2487	$219.25	$219.25	$219.20
Purchase #6	$123.31	11.134%	$137.0393	$137.04	$137.05	$137.00
Purchase #7	$169.69	9.321%	$185.5068	$185.51	$185.50	$185.50
7 purchase totals =	$973.05		$1,065.6941	$1,065.70	$1,065.70	$1,065.50