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	$74.32	12.570%	$83.662	$83.66	$83.65	$83.70
Purchase #2	$196.78	9.430%	$215.3364	$215.34	$215.35	$215.30
Purchase #3	$72.48	13.121%	$81.9901	$81.99	$82.00	$82.00
Purchase #4	$126.87	3.513%	$131.3269	$131.33	$131.35	$131.30
Purchase #5	$151.62	11.754%	$169.4414	$169.44	$169.45	$169.40
Purchase #6	$148.59	3.387%	$153.6227	$153.62	$153.60	$153.60
Purchase #7	$153.55	13.652%	$174.5126	$174.51	$174.50	$174.50
7 purchase totals =	$924.21		$1,009.8921	$1,009.89	$1,009.90	$1,009.80