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	$222.57	3.218%	$229.7323	$229.73	$229.75	$229.70
Purchase #2	$65.56	8.716%	$71.2742	$71.27	$71.25	$71.30
Purchase #3	$88.90	3.180%	$91.727	$91.73	$91.75	$91.70
Purchase #4	$29.81	12.777%	$33.6188	$33.62	$33.60	$33.60
Purchase #5	$85.56	7.458%	$91.9411	$91.94	$91.95	$91.90
Purchase #6	$133.52	4.483%	$139.5057	$139.51	$139.50	$139.50
Purchase #7	$135.56	5.462%	$142.9643	$142.96	$142.95	$143.00
7 purchase totals =	$761.48		$800.7634	$800.76	$800.75	$800.70