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	$141.52	5.208%	$148.8904	$148.89	$148.90	$148.90
Purchase #2	$144.47	12.762%	$162.9073	$162.91	$162.90	$162.90
Purchase #3	$65.91	10.850%	$73.0612	$73.06	$73.05	$73.10
Purchase #4	$56.97	4.735%	$59.6675	$59.67	$59.65	$59.70
Purchase #5	$244.95	11.520%	$273.1682	$273.17	$273.15	$273.20
Purchase #6	$216.42	9.153%	$236.2289	$236.23	$236.25	$236.20
Purchase #7	$174.53	10.308%	$192.5206	$192.52	$192.50	$192.50
7 purchase totals =	$1,044.77		$1,146.4441	$1,146.45	$1,146.40	$1,146.50