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	$143.38	3.557%	$148.48	$148.48	$148.50	$148.50
Purchase #2	$212.34	5.444%	$223.8998	$223.90	$223.90	$223.90
Purchase #3	$89.84	7.582%	$96.6517	$96.65	$96.65	$96.70
Purchase #4	$178.30	10.447%	$196.927	$196.93	$196.95	$196.90
Purchase #5	$41.70	6.249%	$44.3058	$44.31	$44.30	$44.30
Purchase #6	$6.46	10.432%	$7.1339	$7.13	$7.15	$7.10
Purchase #7	$225.35	13.239%	$255.1841	$255.18	$255.20	$255.20
7 purchase totals =	$897.37		$972.5823	$972.58	$972.65	$972.60