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	$76.34	12.684%	$86.023	$86.02	$86.00	$86.00
Purchase #2	$226.72	3.400%	$234.4285	$234.43	$234.45	$234.40
Purchase #3	$21.36	6.348%	$22.7159	$22.72	$22.70	$22.70
Purchase #4	$88.86	13.410%	$100.7761	$100.78	$100.80	$100.80
Purchase #5	$200.73	4.146%	$209.0523	$209.05	$209.05	$209.10
Purchase #6	$239.61	7.199%	$256.8595	$256.86	$256.85	$256.90
Purchase #7	$20.96	6.755%	$22.3758	$22.38	$22.40	$22.40
7 purchase totals =	$874.58		$932.2311	$932.24	$932.25	$932.30