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	$157.90	6.703%	$168.484	$168.48	$168.50	$168.50
Purchase #2	$143.56	6.549%	$152.9617	$152.96	$152.95	$153.00
Purchase #3	$221.71	13.354%	$251.3172	$251.32	$251.30	$251.30
Purchase #4	$46.61	3.801%	$48.3816	$48.38	$48.40	$48.40
Purchase #5	$211.36	5.827%	$223.6759	$223.68	$223.70	$223.70
Purchase #6	$17.68	13.206%	$20.0148	$20.01	$20.00	$20.00
Purchase #7	$199.32	8.116%	$215.4968	$215.50	$215.50	$215.50
7 purchase totals =	$998.14		$1,080.3320	$1,080.33	$1,080.35	$1,080.40