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	$126.53	3.856%	$131.409	$131.41	$131.40	$131.40
Purchase #2	$16.70	12.226%	$18.7417	$18.74	$18.75	$18.70
Purchase #3	$138.46	10.412%	$152.8765	$152.88	$152.90	$152.90
Purchase #4	$164.32	9.242%	$179.5065	$179.51	$179.50	$179.50
Purchase #5	$123.75	3.245%	$127.7657	$127.77	$127.75	$127.80
Purchase #6	$155.91	8.656%	$169.4056	$169.41	$169.40	$169.40
Purchase #7	$18.70	8.637%	$20.3151	$20.32	$20.30	$20.30
7 purchase totals =	$744.37		$800.0201	$800.04	$800.00	$800.00