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	$113.69	3.724%	$117.9238	$117.92	$117.90	$117.90
Purchase #2	$167.96	13.588%	$190.7824	$190.78	$190.80	$190.80
Purchase #3	$187.47	4.846%	$196.5548	$196.55	$196.55	$196.60
Purchase #4	$112.73	11.146%	$125.2949	$125.29	$125.30	$125.30
Purchase #5	$85.89	7.832%	$92.6169	$92.62	$92.60	$92.60
Purchase #6	$106.71	7.499%	$114.7122	$114.71	$114.70	$114.70
Purchase #7	$121.31	8.176%	$131.2283	$131.23	$131.25	$131.20
7 purchase totals =	$895.76		$969.1133	$969.10	$969.10	$969.10