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	$56.95	3.114%	$58.7234	$58.72	$58.70	$58.70
Purchase #2	$231.58	6.489%	$246.6072	$246.61	$246.60	$246.60
Purchase #3	$211.72	12.330%	$237.8251	$237.83	$237.85	$237.80
Purchase #4	$124.25	5.167%	$130.67	$130.67	$130.65	$130.70
Purchase #5	$61.44	5.131%	$64.5925	$64.59	$64.60	$64.60
Purchase #6	$92.46	13.574%	$105.0105	$105.01	$105.00	$105.00
Purchase #7	$188.52	4.395%	$196.8055	$196.81	$196.80	$196.80
7 purchase totals =	$966.92		$1,040.2342	$1,040.24	$1,040.20	$1,040.20