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	$228.54	3.523%	$236.5915	$236.59	$236.60	$236.60
Purchase #2	$16.84	10.236%	$18.5637	$18.56	$18.55	$18.60
Purchase #3	$160.43	6.520%	$170.89	$170.89	$170.90	$170.90
Purchase #4	$37.38	9.394%	$40.8915	$40.89	$40.90	$40.90
Purchase #5	$236.95	3.643%	$245.5821	$245.58	$245.60	$245.60
Purchase #6	$98.54	6.437%	$104.883	$104.88	$104.90	$104.90
Purchase #7	$104.52	9.219%	$114.1557	$114.16	$114.15	$114.20
7 purchase totals =	$883.20		$931.5575	$931.55	$931.60	$931.70