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	$46.68	9.822%	$51.2649	$51.26	$51.25	$51.30
Purchase #2	$161.53	4.511%	$168.8166	$168.82	$168.80	$168.80
Purchase #3	$132.33	5.139%	$139.1304	$139.13	$139.15	$139.10
Purchase #4	$183.65	3.661%	$190.3734	$190.37	$190.35	$190.40
Purchase #5	$124.92	11.305%	$139.0422	$139.04	$139.05	$139.00
Purchase #6	$191.83	12.697%	$216.1867	$216.19	$216.20	$216.20
Purchase #7	$150.85	9.416%	$165.054	$165.05	$165.05	$165.10
7 purchase totals =	$991.79		$1,069.8682	$1,069.86	$1,069.85	$1,069.90