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	$237.71	3.461%	$245.9371	$245.94	$245.95	$245.90
Purchase #2	$160.90	6.838%	$171.9023	$171.90	$171.90	$171.90
Purchase #3	$196.29	13.179%	$222.1591	$222.16	$222.15	$222.20
Purchase #4	$62.56	3.189%	$64.555	$64.56	$64.55	$64.60
Purchase #5	$38.34	4.204%	$39.9518	$39.95	$39.95	$40.00
Purchase #6	$160.78	9.236%	$175.6296	$175.63	$175.65	$175.60
Purchase #7	$161.36	6.228%	$171.4095	$171.41	$171.40	$171.40
7 purchase totals =	$1,017.94		$1,091.5444	$1,091.55	$1,091.55	$1,091.60