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	$53.94	8.674%	$58.6188	$58.62	$58.60	$58.60
Purchase #2	$79.47	3.538%	$82.2816	$82.28	$82.30	$82.30
Purchase #3	$34.54	6.562%	$36.8065	$36.81	$36.80	$36.80
Purchase #4	$142.46	13.633%	$161.8816	$161.88	$161.90	$161.90
Purchase #5	$71.31	10.700%	$78.9402	$78.94	$78.95	$78.90
Purchase #6	$65.44	9.386%	$71.5822	$71.58	$71.60	$71.60
Purchase #7	$132.42	8.351%	$143.4784	$143.48	$143.50	$143.50
7 purchase totals =	$579.58		$633.5893	$633.59	$633.65	$633.60