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	$96.57	6.618%	$102.961	$102.96	$102.95	$103.00
Purchase #2	$207.57	8.720%	$225.6701	$225.67	$225.65	$225.70
Purchase #3	$127.68	11.695%	$142.6122	$142.61	$142.60	$142.60
Purchase #4	$159.29	4.610%	$166.6333	$166.63	$166.65	$166.60
Purchase #5	$130.61	8.382%	$141.5577	$141.56	$141.55	$141.60
Purchase #6	$78.64	11.442%	$87.638	$87.64	$87.65	$87.60
Purchase #7	$127.64	5.682%	$134.8925	$134.89	$134.90	$134.90
7 purchase totals =	$928.00		$1,001.9648	$1,001.96	$1,001.95	$1,002.00