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	$74.98	10.392%	$82.7719	$82.77	$82.75	$82.80
Purchase #2	$101.91	3.428%	$105.4035	$105.40	$105.40	$105.40
Purchase #3	$37.65	9.439%	$41.2038	$41.20	$41.20	$41.20
Purchase #4	$99.90	13.866%	$113.7521	$113.75	$113.75	$113.80
Purchase #5	$221.56	4.688%	$231.9467	$231.95	$231.95	$231.90
Purchase #6	$36.33	3.556%	$37.6219	$37.62	$37.60	$37.60
Purchase #7	$136.84	4.320%	$142.7515	$142.75	$142.75	$142.80
7 purchase totals =	$709.17		$755.4514	$755.44	$755.40	$755.50