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	$199.76	12.865%	$225.4591	$225.46	$225.45	$225.50
Purchase #2	$243.47	11.455%	$271.3595	$271.36	$271.35	$271.40
Purchase #3	$57.77	12.626%	$65.064	$65.06	$65.05	$65.10
Purchase #4	$109.38	7.759%	$117.8668	$117.87	$117.85	$117.90
Purchase #5	$228.55	9.775%	$250.8908	$250.89	$250.90	$250.90
Purchase #6	$38.34	5.155%	$40.3164	$40.32	$40.30	$40.30
Purchase #7	$190.71	9.696%	$209.2012	$209.20	$209.20	$209.20
7 purchase totals =	$1,067.98		$1,180.1578	$1,180.16	$1,180.10	$1,180.30