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	$164.56	4.358%	$171.7315	$171.73	$171.75	$171.70
Purchase #2	$53.86	11.284%	$59.9376	$59.94	$59.95	$59.90
Purchase #3	$204.57	7.602%	$220.1214	$220.12	$220.10	$220.10
Purchase #4	$204.94	12.180%	$229.9017	$229.90	$229.90	$229.90
Purchase #5	$218.55	10.473%	$241.4387	$241.44	$241.45	$241.40
Purchase #6	$230.90	13.838%	$262.8519	$262.85	$262.85	$262.90
Purchase #7	$244.89	5.307%	$257.8863	$257.89	$257.90	$257.90
7 purchase totals =	$1,322.27		$1,443.8691	$1,443.87	$1,443.90	$1,443.80