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	$223.38	10.233%	$246.2385	$246.24	$246.25	$246.20
Purchase #2	$18.55	9.116%	$20.241	$20.24	$20.25	$20.20
Purchase #3	$190.57	9.582%	$208.8304	$208.83	$208.85	$208.80
Purchase #4	$213.61	4.711%	$223.6732	$223.67	$223.65	$223.70
Purchase #5	$218.37	9.436%	$238.9754	$238.98	$239.00	$239.00
Purchase #6	$146.72	5.791%	$155.2166	$155.22	$155.20	$155.20
Purchase #7	$115.78	12.635%	$130.4088	$130.41	$130.40	$130.40
7 purchase totals =	$1,126.98		$1,223.5839	$1,223.59	$1,223.60	$1,223.50