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	$235.76	8.432%	$255.6393	$255.64	$255.65	$255.60
Purchase #2	$10.53	3.403%	$10.8883	$10.89	$10.90	$10.90
Purchase #3	$242.68	12.637%	$273.3475	$273.35	$273.35	$273.30
Purchase #4	$45.30	7.462%	$48.6803	$48.68	$48.70	$48.70
Purchase #5	$209.99	13.234%	$237.7801	$237.78	$237.80	$237.80
Purchase #6	$187.71	4.744%	$196.615	$196.62	$196.60	$196.60
Purchase #7	$136.98	4.113%	$142.614	$142.61	$142.60	$142.60
7 purchase totals =	$1,068.95		$1,165.5645	$1,165.57	$1,165.60	$1,165.50