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	$223.81	5.811%	$236.8156	$236.82	$236.80	$236.80
Purchase #2	$7.59	12.555%	$8.5429	$8.54	$8.55	$8.50
Purchase #3	$52.42	12.339%	$58.8881	$58.89	$58.90	$58.90
Purchase #4	$33.64	5.728%	$35.5669	$35.57	$35.55	$35.60
Purchase #5	$160.65	10.132%	$176.9271	$176.93	$176.95	$176.90
Purchase #6	$92.55	13.460%	$105.0072	$105.01	$105.00	$105.00
Purchase #7	$96.29	4.764%	$100.8773	$100.88	$100.90	$100.90
7 purchase totals =	$666.95		$722.6251	$722.64	$722.65	$722.60