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	$104.35	7.660%	$112.3432	$112.34	$112.35	$112.30
Purchase #2	$98.49	10.790%	$109.1171	$109.12	$109.10	$109.10
Purchase #3	$38.51	11.384%	$42.894	$42.89	$42.90	$42.90
Purchase #4	$78.62	3.713%	$81.5392	$81.54	$81.55	$81.50
Purchase #5	$233.45	10.193%	$257.2456	$257.25	$257.25	$257.20
Purchase #6	$11.78	13.531%	$13.374	$13.37	$13.35	$13.40
Purchase #7	$227.30	11.782%	$254.0805	$254.08	$254.10	$254.10
7 purchase totals =	$792.50		$870.5936	$870.59	$870.60	$870.50