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	$51.95	10.689%	$57.5029	$57.50	$57.50	$57.50
Purchase #2	$17.62	4.529%	$18.418	$18.42	$18.40	$18.40
Purchase #3	$37.37	10.489%	$41.2897	$41.29	$41.30	$41.30
Purchase #4	$234.97	3.285%	$242.6888	$242.69	$242.70	$242.70
Purchase #5	$152.51	10.163%	$168.0096	$168.01	$168.00	$168.00
Purchase #6	$247.76	12.780%	$279.4237	$279.42	$279.40	$279.40
Purchase #7	$183.61	9.261%	$200.6141	$200.61	$200.60	$200.60
7 purchase totals =	$925.79		$1,007.9468	$1,007.94	$1,007.90	$1,007.90