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	$34.74	6.582%	$37.0266	$37.03	$37.05	$37.00
Purchase #2	$148.38	12.693%	$167.2139	$167.21	$167.20	$167.20
Purchase #3	$112.66	10.491%	$124.4792	$124.48	$124.50	$124.50
Purchase #4	$213.26	9.682%	$233.9078	$233.91	$233.90	$233.90
Purchase #5	$228.45	5.766%	$241.6224	$241.62	$241.60	$241.60
Purchase #6	$221.84	5.240%	$233.4644	$233.46	$233.45	$233.50
Purchase #7	$200.32	3.114%	$206.558	$206.56	$206.55	$206.60
7 purchase totals =	$1,159.65		$1,244.2723	$1,244.27	$1,244.25	$1,244.30