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	$89.34	6.357%	$95.0193	$95.02	$95.00	$95.00
Purchase #2	$39.46	9.537%	$43.2233	$43.22	$43.20	$43.20
Purchase #3	$75.84	8.465%	$82.2599	$82.26	$82.25	$82.30
Purchase #4	$155.34	7.535%	$167.0449	$167.04	$167.05	$167.00
Purchase #5	$206.27	5.309%	$217.2209	$217.22	$217.20	$217.20
Purchase #6	$40.81	5.684%	$43.1296	$43.13	$43.15	$43.10
Purchase #7	$104.31	7.311%	$111.9361	$111.94	$111.95	$111.90
7 purchase totals =	$711.37		$759.8340	$759.83	$759.80	$759.70