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	$88.45	11.451%	$98.5784	$98.58	$98.60	$98.60
Purchase #2	$71.39	13.836%	$81.2675	$81.27	$81.25	$81.30
Purchase #3	$90.37	12.300%	$101.4855	$101.49	$101.50	$101.50
Purchase #4	$62.34	7.241%	$66.854	$66.85	$66.85	$66.90
Purchase #5	$193.85	11.623%	$216.3812	$216.38	$216.40	$216.40
Purchase #6	$11.90	10.170%	$13.1102	$13.11	$13.10	$13.10
Purchase #7	$119.59	11.675%	$133.5521	$133.55	$133.55	$133.60
7 purchase totals =	$637.89		$711.2289	$711.23	$711.25	$711.40