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	$132.29	12.835%	$149.2694	$149.27	$149.25	$149.30
Purchase #2	$11.30	5.194%	$11.8869	$11.89	$11.90	$11.90
Purchase #3	$176.38	13.109%	$199.5017	$199.50	$199.50	$199.50
Purchase #4	$56.65	12.508%	$63.7358	$63.74	$63.75	$63.70
Purchase #5	$118.53	6.703%	$126.4751	$126.48	$126.50	$126.50
Purchase #6	$39.83	3.303%	$41.1456	$41.15	$41.15	$41.10
Purchase #7	$81.53	9.617%	$89.3707	$89.37	$89.35	$89.40
7 purchase totals =	$616.51		$681.3852	$681.40	$681.40	$681.40