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	$242.89	8.445%	$263.4021	$263.40	$263.40	$263.40
Purchase #2	$185.25	5.850%	$196.0871	$196.09	$196.10	$196.10
Purchase #3	$35.98	9.281%	$39.3193	$39.32	$39.30	$39.30
Purchase #4	$34.67	10.811%	$38.4182	$38.42	$38.40	$38.40
Purchase #5	$163.57	4.799%	$171.4197	$171.42	$171.40	$171.40
Purchase #6	$227.33	12.182%	$255.0233	$255.02	$255.00	$255.00
Purchase #7	$152.86	4.727%	$160.0857	$160.09	$160.10	$160.10
7 purchase totals =	$1,042.55		$1,123.7554	$1,123.76	$1,123.70	$1,123.70