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	$200.73	12.682%	$226.1866	$226.19	$226.20	$226.20
Purchase #2	$52.33	10.568%	$57.8602	$57.86	$57.85	$57.90
Purchase #3	$69.47	4.795%	$72.8011	$72.80	$72.80	$72.80
Purchase #4	$216.64	13.629%	$246.1659	$246.17	$246.15	$246.20
Purchase #5	$187.72	6.488%	$199.8993	$199.90	$199.90	$199.90
Purchase #6	$143.37	5.191%	$150.8123	$150.81	$150.80	$150.80
Purchase #7	$35.30	8.576%	$38.3273	$38.33	$38.35	$38.30
7 purchase totals =	$905.56		$992.0527	$992.06	$992.05	$992.10