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	$35.31	13.529%	$40.0871	$40.09	$40.10	$40.10
Purchase #2	$50.76	6.265%	$53.9401	$53.94	$53.95	$53.90
Purchase #3	$206.51	10.870%	$228.9576	$228.96	$228.95	$229.00
Purchase #4	$76.81	12.842%	$86.6739	$86.67	$86.65	$86.70
Purchase #5	$190.82	10.590%	$211.0278	$211.03	$211.05	$211.00
Purchase #6	$235.74	8.391%	$255.5209	$255.52	$255.50	$255.50
Purchase #7	$133.36	11.177%	$148.2656	$148.27	$148.25	$148.30
7 purchase totals =	$929.31		$1,024.4730	$1,024.48	$1,024.45	$1,024.50