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	$74.47	3.742%	$77.2567	$77.26	$77.25	$77.30
Purchase #2	$245.35	4.627%	$256.7023	$256.70	$256.70	$256.70
Purchase #3	$106.88	6.471%	$113.7962	$113.80	$113.80	$113.80
Purchase #4	$182.59	7.776%	$196.7882	$196.79	$196.80	$196.80
Purchase #5	$162.97	5.855%	$172.5119	$172.51	$172.50	$172.50
Purchase #6	$168.77	11.449%	$188.0925	$188.09	$188.10	$188.10
Purchase #7	$105.43	11.403%	$117.4522	$117.45	$117.45	$117.50
7 purchase totals =	$1,046.46		$1,122.6000	$1,122.60	$1,122.60	$1,122.70