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	$175.48	12.152%	$196.8043	$196.80	$196.80	$196.80
Purchase #2	$90.62	13.686%	$103.0223	$103.02	$103.00	$103.00
Purchase #3	$54.41	4.495%	$56.8557	$56.86	$56.85	$56.90
Purchase #4	$217.41	9.848%	$238.8205	$238.82	$238.80	$238.80
Purchase #5	$101.77	3.141%	$104.9666	$104.97	$104.95	$105.00
Purchase #6	$94.78	8.164%	$102.5178	$102.52	$102.50	$102.50
Purchase #7	$170.39	8.854%	$185.4763	$185.48	$185.50	$185.50
7 purchase totals =	$904.86		$988.4635	$988.47	$988.40	$988.50