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	$108.38	4.106%	$112.8301	$112.83	$112.85	$112.80
Purchase #2	$184.50	12.668%	$207.8725	$207.87	$207.85	$207.90
Purchase #3	$152.29	6.609%	$162.3548	$162.35	$162.35	$162.40
Purchase #4	$71.49	9.350%	$78.1743	$78.17	$78.15	$78.20
Purchase #5	$187.57	13.722%	$213.3084	$213.31	$213.30	$213.30
Purchase #6	$53.46	3.683%	$55.4289	$55.43	$55.45	$55.40
Purchase #7	$204.88	7.813%	$220.8873	$220.89	$220.90	$220.90
7 purchase totals =	$962.57		$1,050.8563	$1,050.85	$1,050.85	$1,050.90