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	$188.34	6.542%	$200.6612	$200.66	$200.65	$200.70
Purchase #2	$146.27	13.214%	$165.5981	$165.60	$165.60	$165.60
Purchase #3	$189.57	6.807%	$202.474	$202.47	$202.45	$202.50
Purchase #4	$45.45	3.468%	$47.0262	$47.03	$47.05	$47.00
Purchase #5	$130.87	10.691%	$144.8613	$144.86	$144.85	$144.90
Purchase #6	$203.34	8.232%	$220.0789	$220.08	$220.10	$220.10
Purchase #7	$78.32	13.784%	$89.1156	$89.12	$89.10	$89.10
7 purchase totals =	$982.16		$1,069.8153	$1,069.82	$1,069.80	$1,069.90