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	$216.27	4.597%	$226.2119	$226.21	$226.20	$226.20
Purchase #2	$197.38	10.614%	$218.3299	$218.33	$218.35	$218.30
Purchase #3	$136.48	5.840%	$144.4504	$144.45	$144.45	$144.50
Purchase #4	$130.61	8.613%	$141.8594	$141.86	$141.85	$141.90
Purchase #5	$142.95	13.759%	$162.6185	$162.62	$162.60	$162.60
Purchase #6	$211.44	5.456%	$222.9762	$222.98	$223.00	$223.00
Purchase #7	$240.39	9.316%	$262.7847	$262.78	$262.80	$262.80
7 purchase totals =	$1,275.52		$1,379.2310	$1,379.23	$1,379.25	$1,379.30