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	$55.55	11.140%	$61.7383	$61.74	$61.75	$61.70
Purchase #2	$171.71	4.444%	$179.3408	$179.34	$179.35	$179.30
Purchase #3	$152.80	13.126%	$172.8565	$172.86	$172.85	$172.90
Purchase #4	$232.69	5.618%	$245.7625	$245.76	$245.75	$245.80
Purchase #5	$163.33	13.788%	$185.8499	$185.85	$185.85	$185.80
Purchase #6	$230.64	9.447%	$252.4286	$252.43	$252.45	$252.40
Purchase #7	$132.64	6.171%	$140.8252	$140.83	$140.85	$140.80
7 purchase totals =	$1,139.36		$1,238.8018	$1,238.81	$1,238.85	$1,238.70