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	$68.33	6.764%	$72.9518	$72.95	$72.95	$73.00
Purchase #2	$117.66	9.480%	$128.8142	$128.81	$128.80	$128.80
Purchase #3	$87.73	8.113%	$94.8475	$94.85	$94.85	$94.80
Purchase #4	$167.31	11.774%	$187.0091	$187.01	$187.00	$187.00
Purchase #5	$179.83	5.696%	$190.0731	$190.07	$190.05	$190.10
Purchase #6	$98.51	5.392%	$103.8217	$103.82	$103.80	$103.80
Purchase #7	$80.68	7.693%	$86.8867	$86.89	$86.90	$86.90
7 purchase totals =	$800.05		$864.4041	$864.40	$864.35	$864.40