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	$214.85	8.552%	$233.224	$233.22	$233.20	$233.20
Purchase #2	$177.33	7.735%	$191.0465	$191.05	$191.05	$191.00
Purchase #3	$82.30	8.448%	$89.2527	$89.25	$89.25	$89.30
Purchase #4	$187.41	11.444%	$208.8572	$208.86	$208.85	$208.90
Purchase #5	$175.72	8.842%	$191.2572	$191.26	$191.25	$191.30
Purchase #6	$160.96	13.259%	$182.3017	$182.30	$182.30	$182.30
Purchase #7	$241.72	7.517%	$259.8901	$259.89	$259.90	$259.90
7 purchase totals =	$1,240.29		$1,355.8294	$1,355.83	$1,355.80	$1,355.90