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	$84.77	9.621%	$92.9257	$92.93	$92.95	$92.90
Purchase #2	$198.65	12.263%	$223.0104	$223.01	$223.00	$223.00
Purchase #3	$37.90	12.421%	$42.6076	$42.61	$42.60	$42.60
Purchase #4	$175.59	9.623%	$192.487	$192.49	$192.50	$192.50
Purchase #5	$199.49	8.621%	$216.688	$216.69	$216.70	$216.70
Purchase #6	$241.74	3.358%	$249.8576	$249.86	$249.85	$249.90
Purchase #7	$90.81	7.794%	$97.8877	$97.89	$97.90	$97.90
7 purchase totals =	$1,028.95		$1,115.4640	$1,115.48	$1,115.50	$1,115.50