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	$74.90	10.468%	$82.7405	$82.74	$82.75	$82.70
Purchase #2	$250.66	11.185%	$278.6963	$278.70	$278.70	$278.70
Purchase #3	$118.70	12.836%	$133.9363	$133.94	$133.95	$133.90
Purchase #4	$163.41	6.103%	$173.3829	$173.38	$173.40	$173.40
Purchase #5	$231.33	10.557%	$255.7515	$255.75	$255.75	$255.80
Purchase #6	$184.33	6.804%	$196.8718	$196.87	$196.85	$196.90
Purchase #7	$9.59	3.451%	$9.921	$9.92	$9.90	$9.90
7 purchase totals =	$1,032.92		$1,131.3003	$1,131.30	$1,131.30	$1,131.30