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	$200.59	10.510%	$221.672	$221.67	$221.65	$221.70
Purchase #2	$133.69	13.613%	$151.8892	$151.89	$151.90	$151.90
Purchase #3	$196.89	6.610%	$209.9044	$209.90	$209.90	$209.90
Purchase #4	$35.26	13.456%	$40.0046	$40.00	$40.00	$40.00
Purchase #5	$142.40	4.510%	$148.8222	$148.82	$148.80	$148.80
Purchase #6	$126.69	5.739%	$133.9607	$133.96	$133.95	$134.00
Purchase #7	$100.38	4.479%	$104.876	$104.88	$104.90	$104.90
7 purchase totals =	$935.90		$1,011.1291	$1,011.12	$1,011.10	$1,011.20