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	$97.98	7.309%	$105.1414	$105.14	$105.15	$105.10
Purchase #2	$18.27	11.470%	$20.3656	$20.37	$20.35	$20.40
Purchase #3	$23.47	5.249%	$24.7019	$24.70	$24.70	$24.70
Purchase #4	$128.37	11.139%	$142.6691	$142.67	$142.65	$142.70
Purchase #5	$94.66	11.645%	$105.6832	$105.68	$105.70	$105.70
Purchase #6	$36.90	12.197%	$41.4007	$41.40	$41.40	$41.40
Purchase #7	$77.69	11.285%	$86.4573	$86.46	$86.45	$86.50
7 purchase totals =	$477.34		$526.4192	$526.42	$526.40	$526.50