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	$43.91	5.104%	$46.1512	$46.15	$46.15	$46.20
Purchase #2	$64.60	12.715%	$72.8139	$72.81	$72.80	$72.80
Purchase #3	$250.58	13.718%	$284.9546	$284.95	$284.95	$285.00
Purchase #4	$150.66	11.192%	$167.5219	$167.52	$167.50	$167.50
Purchase #5	$90.37	4.632%	$94.5559	$94.56	$94.55	$94.60
Purchase #6	$131.77	4.262%	$137.386	$137.39	$137.40	$137.40
Purchase #7	$79.69	12.758%	$89.8569	$89.86	$89.85	$89.90
7 purchase totals =	$811.58		$893.2404	$893.24	$893.20	$893.40