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	$200.64	6.310%	$213.3004	$213.30	$213.30	$213.30
Purchase #2	$61.80	6.443%	$65.7818	$65.78	$65.80	$65.80
Purchase #3	$103.73	13.327%	$117.5541	$117.55	$117.55	$117.60
Purchase #4	$44.28	12.698%	$49.9027	$49.90	$49.90	$49.90
Purchase #5	$40.27	13.377%	$45.6569	$45.66	$45.65	$45.70
Purchase #6	$91.60	10.238%	$100.978	$100.98	$101.00	$101.00
Purchase #7	$96.37	7.308%	$103.4127	$103.41	$103.40	$103.40
7 purchase totals =	$638.69		$696.5866	$696.58	$696.60	$696.70