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	$219.61	3.589%	$227.4918	$227.49	$227.50	$227.50
Purchase #2	$143.49	9.333%	$156.8819	$156.88	$156.90	$156.90
Purchase #3	$166.30	7.152%	$178.1938	$178.19	$178.20	$178.20
Purchase #4	$74.95	10.165%	$82.5687	$82.57	$82.55	$82.60
Purchase #5	$209.80	7.572%	$225.6861	$225.69	$225.70	$225.70
Purchase #6	$189.75	3.341%	$196.0895	$196.09	$196.10	$196.10
Purchase #7	$213.66	4.745%	$223.7982	$223.80	$223.80	$223.80
7 purchase totals =	$1,217.56		$1,290.7100	$1,290.71	$1,290.75	$1,290.80