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	$243.57	4.687%	$254.9861	$254.99	$255.00	$255.00
Purchase #2	$214.66	13.315%	$243.242	$243.24	$243.25	$243.20
Purchase #3	$109.85	3.245%	$113.4146	$113.41	$113.40	$113.40
Purchase #4	$146.93	10.489%	$162.3415	$162.34	$162.35	$162.30
Purchase #5	$117.65	11.802%	$131.5351	$131.54	$131.55	$131.50
Purchase #6	$54.61	5.342%	$57.5273	$57.53	$57.55	$57.50
Purchase #7	$103.55	6.726%	$110.5148	$110.51	$110.50	$110.50
7 purchase totals =	$990.82		$1,073.5614	$1,073.56	$1,073.60	$1,073.40