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	$197.45	5.434%	$208.1794	$208.18	$208.20	$208.20
Purchase #2	$67.46	7.535%	$72.5431	$72.54	$72.55	$72.50
Purchase #3	$39.70	7.499%	$42.6771	$42.68	$42.70	$42.70
Purchase #4	$139.82	6.369%	$148.7251	$148.73	$148.75	$148.70
Purchase #5	$110.79	6.792%	$118.3149	$118.31	$118.30	$118.30
Purchase #6	$107.84	4.526%	$112.7208	$112.72	$112.70	$112.70
Purchase #7	$154.38	6.256%	$164.038	$164.04	$164.05	$164.00
7 purchase totals =	$817.44		$867.1984	$867.20	$867.25	$867.10