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	$119.50	6.676%	$127.4778	$127.48	$127.50	$127.50
Purchase #2	$19.57	4.437%	$20.4383	$20.44	$20.45	$20.40
Purchase #3	$220.75	3.388%	$228.229	$228.23	$228.25	$228.20
Purchase #4	$11.49	13.216%	$13.0085	$13.01	$13.00	$13.00
Purchase #5	$104.89	13.314%	$118.8551	$118.86	$118.85	$118.90
Purchase #6	$13.98	11.168%	$15.5413	$15.54	$15.55	$15.50
Purchase #7	$74.97	4.504%	$78.3466	$78.35	$78.35	$78.30
7 purchase totals =	$565.15		$601.8966	$601.91	$601.95	$601.80