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	$125.59	12.874%	$141.7585	$141.76	$141.75	$141.80
Purchase #2	$31.29	10.568%	$34.5967	$34.60	$34.60	$34.60
Purchase #3	$188.41	8.598%	$204.6095	$204.61	$204.60	$204.60
Purchase #4	$179.63	9.267%	$196.2763	$196.28	$196.30	$196.30
Purchase #5	$101.72	3.245%	$105.0208	$105.02	$105.00	$105.00
Purchase #6	$57.60	8.460%	$62.473	$62.47	$62.45	$62.50
Purchase #7	$186.36	10.661%	$206.2278	$206.23	$206.25	$206.20
7 purchase totals =	$870.60		$950.9626	$950.97	$950.95	$951.00