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	$155.46	6.542%	$165.6302	$165.63	$165.65	$165.60
Purchase #2	$239.83	5.475%	$252.9607	$252.96	$252.95	$253.00
Purchase #3	$236.74	13.445%	$268.5697	$268.57	$268.55	$268.60
Purchase #4	$217.76	11.773%	$243.3969	$243.40	$243.40	$243.40
Purchase #5	$227.90	12.538%	$256.4741	$256.47	$256.45	$256.50
Purchase #6	$182.50	7.644%	$196.4503	$196.45	$196.45	$196.50
Purchase #7	$92.28	13.630%	$104.8578	$104.86	$104.85	$104.90
7 purchase totals =	$1,352.47		$1,488.3397	$1,488.34	$1,488.30	$1,488.50