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	$120.79	5.678%	$127.6485	$127.65	$127.65	$127.60
Purchase #2	$185.63	4.484%	$193.9536	$193.95	$193.95	$194.00
Purchase #3	$168.98	10.649%	$186.9747	$186.97	$186.95	$187.00
Purchase #4	$86.47	13.844%	$98.4409	$98.44	$98.45	$98.40
Purchase #5	$217.89	4.457%	$227.6014	$227.60	$227.60	$227.60
Purchase #6	$123.89	6.397%	$131.8152	$131.82	$131.80	$131.80
Purchase #7	$123.37	6.510%	$131.4014	$131.40	$131.40	$131.40
7 purchase totals =	$1,027.02		$1,097.8357	$1,097.83	$1,097.80	$1,097.80