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	$38.97	11.569%	$43.4784	$43.48	$43.50	$43.50
Purchase #2	$187.35	6.129%	$198.8327	$198.83	$198.85	$198.80
Purchase #3	$60.30	8.591%	$65.4804	$65.48	$65.50	$65.50
Purchase #4	$132.65	13.228%	$150.1969	$150.20	$150.20	$150.20
Purchase #5	$75.66	12.354%	$85.007	$85.01	$85.00	$85.00
Purchase #6	$142.40	12.300%	$159.9152	$159.92	$159.90	$159.90
Purchase #7	$54.47	3.607%	$56.4347	$56.43	$56.45	$56.40
7 purchase totals =	$691.80		$759.3453	$759.35	$759.40	$759.30