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	$108.78	5.223%	$114.4616	$114.46	$114.45	$114.50
Purchase #2	$53.40	8.203%	$57.7804	$57.78	$57.80	$57.80
Purchase #3	$177.90	12.497%	$200.1322	$200.13	$200.15	$200.10
Purchase #4	$238.46	11.357%	$265.5419	$265.54	$265.55	$265.50
Purchase #5	$27.39	12.746%	$30.8811	$30.88	$30.90	$30.90
Purchase #6	$99.59	4.569%	$104.1403	$104.14	$104.15	$104.10
Purchase #7	$196.35	7.378%	$210.8367	$210.84	$210.85	$210.80
7 purchase totals =	$901.87		$983.7742	$983.77	$983.85	$983.70