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	$129.87	10.796%	$143.8908	$143.89	$143.90	$143.90
Purchase #2	$229.54	10.549%	$253.7542	$253.75	$253.75	$253.80
Purchase #3	$91.71	6.795%	$97.9417	$97.94	$97.95	$97.90
Purchase #4	$191.84	5.474%	$202.3413	$202.34	$202.35	$202.30
Purchase #5	$82.98	9.248%	$90.654	$90.65	$90.65	$90.70
Purchase #6	$119.62	3.294%	$123.5603	$123.56	$123.55	$123.60
Purchase #7	$41.37	3.691%	$42.897	$42.90	$42.90	$42.90
7 purchase totals =	$886.93		$955.0393	$955.03	$955.05	$955.10