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	$117.27	8.839%	$127.6355	$127.64	$127.65	$127.60
Purchase #2	$183.36	11.526%	$204.4941	$204.49	$204.50	$204.50
Purchase #3	$168.87	3.549%	$174.8632	$174.86	$174.85	$174.90
Purchase #4	$40.42	4.283%	$42.1512	$42.15	$42.15	$42.20
Purchase #5	$199.53	5.670%	$210.8434	$210.84	$210.85	$210.80
Purchase #6	$29.94	12.568%	$33.7029	$33.70	$33.70	$33.70
Purchase #7	$114.77	10.534%	$126.8599	$126.86	$126.85	$126.90
7 purchase totals =	$854.16		$920.5502	$920.54	$920.55	$920.60