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	$49.59	12.223%	$55.6514	$55.65	$55.65	$55.70
Purchase #2	$74.46	3.244%	$76.8755	$76.88	$76.90	$76.90
Purchase #3	$75.55	9.472%	$82.7061	$82.71	$82.70	$82.70
Purchase #4	$160.32	5.665%	$169.4021	$169.40	$169.40	$169.40
Purchase #5	$154.29	4.438%	$161.1374	$161.14	$161.15	$161.10
Purchase #6	$34.89	8.740%	$37.9394	$37.94	$37.95	$37.90
Purchase #7	$89.32	5.430%	$94.1701	$94.17	$94.15	$94.20
7 purchase totals =	$638.42		$677.8820	$677.89	$677.90	$677.90