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	$114.40	4.288%	$119.3055	$119.31	$119.30	$119.30
Purchase #2	$49.59	6.616%	$52.8709	$52.87	$52.85	$52.90
Purchase #3	$74.96	4.188%	$78.0993	$78.10	$78.10	$78.10
Purchase #4	$196.87	10.376%	$217.2972	$217.30	$217.30	$217.30
Purchase #5	$31.51	13.711%	$35.8303	$35.83	$35.85	$35.80
Purchase #6	$46.90	9.444%	$51.3292	$51.33	$51.35	$51.30
Purchase #7	$133.73	9.840%	$146.889	$146.89	$146.90	$146.90
7 purchase totals =	$647.96		$701.6214	$701.63	$701.65	$701.60