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	$38.58	5.437%	$40.6776	$40.68	$40.70	$40.70
Purchase #2	$98.54	6.537%	$104.9816	$104.98	$105.00	$105.00
Purchase #3	$40.31	12.490%	$45.3447	$45.34	$45.35	$45.30
Purchase #4	$181.46	8.119%	$196.1927	$196.19	$196.20	$196.20
Purchase #5	$40.95	4.742%	$42.8918	$42.89	$42.90	$42.90
Purchase #6	$242.47	5.126%	$254.899	$254.90	$254.90	$254.90
Purchase #7	$55.97	5.447%	$59.0187	$59.02	$59.00	$59.00
7 purchase totals =	$698.28		$744.0061	$744.00	$744.05	$744.00