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	$103.63	8.813%	$112.7629	$112.76	$112.75	$112.80
Purchase #2	$52.56	10.293%	$57.97	$57.97	$57.95	$58.00
Purchase #3	$176.32	11.712%	$196.9706	$196.97	$196.95	$197.00
Purchase #4	$164.39	5.131%	$172.8249	$172.82	$172.80	$172.80
Purchase #5	$207.86	5.189%	$218.6459	$218.65	$218.65	$218.60
Purchase #6	$95.74	6.237%	$101.7113	$101.71	$101.70	$101.70
Purchase #7	$57.32	4.479%	$59.8874	$59.89	$59.90	$59.90
7 purchase totals =	$857.82		$920.7730	$920.77	$920.70	$920.80