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	$242.42	9.533%	$265.5299	$265.53	$265.55	$265.50
Purchase #2	$10.76	7.719%	$11.5906	$11.59	$11.60	$11.60
Purchase #3	$109.90	6.623%	$117.1787	$117.18	$117.20	$117.20
Purchase #4	$28.83	9.391%	$31.5374	$31.54	$31.55	$31.50
Purchase #5	$156.86	3.451%	$162.2732	$162.27	$162.25	$162.30
Purchase #6	$221.97	10.411%	$245.0793	$245.08	$245.10	$245.10
Purchase #7	$236.51	11.600%	$263.9452	$263.95	$263.95	$263.90
7 purchase totals =	$1,007.25		$1,097.1343	$1,097.14	$1,097.20	$1,097.10