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	$190.69	6.789%	$203.6359	$203.64	$203.65	$203.60
Purchase #2	$246.79	3.475%	$255.366	$255.37	$255.35	$255.40
Purchase #3	$159.61	5.353%	$168.1539	$168.15	$168.15	$168.20
Purchase #4	$105.72	3.785%	$109.7215	$109.72	$109.70	$109.70
Purchase #5	$51.59	10.537%	$57.026	$57.03	$57.05	$57.00
Purchase #6	$131.86	6.851%	$140.8937	$140.89	$140.90	$140.90
Purchase #7	$9.88	13.488%	$11.2126	$11.21	$11.20	$11.20
7 purchase totals =	$896.14		$946.0096	$946.01	$946.00	$946.00