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	$223.44	8.719%	$242.9217	$242.92	$242.90	$242.90
Purchase #2	$157.34	4.654%	$164.6626	$164.66	$164.65	$164.70
Purchase #3	$175.83	8.338%	$190.4907	$190.49	$190.50	$190.50
Purchase #4	$155.33	8.487%	$168.5129	$168.51	$168.50	$168.50
Purchase #5	$30.52	7.803%	$32.9015	$32.90	$32.90	$32.90
Purchase #6	$150.81	12.546%	$169.7306	$169.73	$169.75	$169.70
Purchase #7	$52.60	5.575%	$55.5325	$55.53	$55.55	$55.50
7 purchase totals =	$945.87		$1,024.7525	$1,024.74	$1,024.75	$1,024.70