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	$152.63	10.607%	$168.8195	$168.82	$168.80	$168.80
Purchase #2	$164.71	8.231%	$178.2673	$178.27	$178.25	$178.30
Purchase #3	$48.35	7.361%	$51.909	$51.91	$51.90	$51.90
Purchase #4	$234.61	11.620%	$261.8717	$261.87	$261.85	$261.90
Purchase #5	$126.33	10.678%	$139.8195	$139.82	$139.80	$139.80
Purchase #6	$210.65	10.540%	$232.8525	$232.85	$232.85	$232.90
Purchase #7	$57.41	11.354%	$63.9283	$63.93	$63.95	$63.90
7 purchase totals =	$994.69		$1,097.4678	$1,097.47	$1,097.40	$1,097.50