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	$142.79	5.172%	$150.1751	$150.18	$150.20	$150.20
Purchase #2	$159.93	4.520%	$167.1588	$167.16	$167.15	$167.20
Purchase #3	$237.80	11.609%	$265.4062	$265.41	$265.40	$265.40
Purchase #4	$30.51	7.429%	$32.7766	$32.78	$32.80	$32.80
Purchase #5	$161.38	9.505%	$176.7192	$176.72	$176.70	$176.70
Purchase #6	$212.60	4.375%	$221.9013	$221.90	$221.90	$221.90
Purchase #7	$196.25	6.331%	$208.6746	$208.67	$208.65	$208.70
7 purchase totals =	$1,141.26		$1,222.8118	$1,222.82	$1,222.80	$1,222.90