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	$69.67	8.270%	$75.4317	$75.43	$75.45	$75.40
Purchase #2	$41.60	3.400%	$43.0144	$43.01	$43.00	$43.00
Purchase #3	$82.97	12.684%	$93.4939	$93.49	$93.50	$93.50
Purchase #4	$192.90	11.738%	$215.5426	$215.54	$215.55	$215.50
Purchase #5	$45.79	5.544%	$48.3286	$48.33	$48.35	$48.30
Purchase #6	$182.92	4.587%	$191.3105	$191.31	$191.30	$191.30
Purchase #7	$151.46	10.298%	$167.0574	$167.06	$167.05	$167.10
7 purchase totals =	$767.31		$834.1791	$834.17	$834.20	$834.10