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	$207.33	7.787%	$223.4748	$223.47	$223.45	$223.50
Purchase #2	$145.45	5.794%	$153.8774	$153.88	$153.90	$153.90
Purchase #3	$40.48	11.208%	$45.017	$45.02	$45.00	$45.00
Purchase #4	$76.31	4.506%	$79.7485	$79.75	$79.75	$79.70
Purchase #5	$69.53	11.626%	$77.6136	$77.61	$77.60	$77.60
Purchase #6	$190.82	4.112%	$198.6665	$198.67	$198.65	$198.70
Purchase #7	$33.76	8.134%	$36.506	$36.51	$36.50	$36.50
7 purchase totals =	$763.68		$814.9038	$814.91	$814.85	$814.90