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	$247.90	8.692%	$269.4475	$269.45	$269.45	$269.40
Purchase #2	$172.44	6.442%	$183.5486	$183.55	$183.55	$183.50
Purchase #3	$7.36	7.395%	$7.9043	$7.90	$7.90	$7.90
Purchase #4	$153.37	13.786%	$174.5136	$174.51	$174.50	$174.50
Purchase #5	$166.97	10.869%	$185.118	$185.12	$185.10	$185.10
Purchase #6	$173.80	6.679%	$185.4081	$185.41	$185.40	$185.40
Purchase #7	$177.87	10.308%	$196.2048	$196.20	$196.20	$196.20
7 purchase totals =	$1,099.71		$1,202.1449	$1,202.14	$1,202.10	$1,202.00