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	$71.61	7.521%	$76.9958	$77.00	$77.00	$77.00
Purchase #2	$199.76	4.571%	$208.891	$208.89	$208.90	$208.90
Purchase #3	$195.98	13.527%	$222.4902	$222.49	$222.50	$222.50
Purchase #4	$51.55	9.836%	$56.6205	$56.62	$56.60	$56.60
Purchase #5	$238.44	7.806%	$257.0526	$257.05	$257.05	$257.10
Purchase #6	$14.87	5.720%	$15.7206	$15.72	$15.70	$15.70
Purchase #7	$240.83	6.214%	$255.7952	$255.80	$255.80	$255.80
7 purchase totals =	$1,013.04		$1,093.5659	$1,093.57	$1,093.55	$1,093.60