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	$209.63	6.130%	$222.4803	$222.48	$222.50	$222.50
Purchase #2	$107.69	12.789%	$121.4625	$121.46	$121.45	$121.50
Purchase #3	$15.63	12.232%	$17.5419	$17.54	$17.55	$17.50
Purchase #4	$100.71	6.111%	$106.8644	$106.86	$106.85	$106.90
Purchase #5	$28.88	8.569%	$31.3547	$31.35	$31.35	$31.40
Purchase #6	$240.29	10.834%	$266.323	$266.32	$266.30	$266.30
Purchase #7	$242.52	6.598%	$258.5215	$258.52	$258.50	$258.50
7 purchase totals =	$945.35		$1,024.5483	$1,024.53	$1,024.50	$1,024.60