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	$132.26	5.274%	$139.2354	$139.24	$139.25	$139.20
Purchase #2	$245.41	4.809%	$257.2118	$257.21	$257.20	$257.20
Purchase #3	$19.81	3.474%	$20.4982	$20.50	$20.50	$20.50
Purchase #4	$133.39	13.163%	$150.9481	$150.95	$150.95	$150.90
Purchase #5	$178.54	3.657%	$185.0692	$185.07	$185.05	$185.10
Purchase #6	$40.83	11.144%	$45.3801	$45.38	$45.40	$45.40
Purchase #7	$132.34	11.266%	$147.2494	$147.25	$147.25	$147.20
7 purchase totals =	$882.58		$945.5922	$945.60	$945.60	$945.50