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	$182.38	10.856%	$202.1792	$202.18	$202.20	$202.20
Purchase #2	$107.95	3.675%	$111.9172	$111.92	$111.90	$111.90
Purchase #3	$118.35	5.693%	$125.0877	$125.09	$125.10	$125.10
Purchase #4	$88.89	13.725%	$101.0902	$101.09	$101.10	$101.10
Purchase #5	$98.92	6.625%	$105.4735	$105.47	$105.45	$105.50
Purchase #6	$123.30	6.214%	$130.9619	$130.96	$130.95	$131.00
Purchase #7	$210.88	5.598%	$222.6851	$222.69	$222.70	$222.70
7 purchase totals =	$930.67		$999.3948	$999.40	$999.40	$999.50