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	$167.84	13.866%	$191.1127	$191.11	$191.10	$191.10
Purchase #2	$203.59	10.790%	$225.5574	$225.56	$225.55	$225.60
Purchase #3	$99.61	3.371%	$102.9679	$102.97	$102.95	$103.00
Purchase #4	$161.39	11.213%	$179.4867	$179.49	$179.50	$179.50
Purchase #5	$217.41	8.737%	$236.4051	$236.41	$236.40	$236.40
Purchase #6	$151.39	11.622%	$168.9845	$168.98	$169.00	$169.00
Purchase #7	$77.33	10.524%	$85.4682	$85.47	$85.45	$85.50
7 purchase totals =	$1,078.56		$1,189.9825	$1,189.99	$1,189.95	$1,190.10