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	$227.90	12.621%	$256.6633	$256.66	$256.65	$256.70
Purchase #2	$174.82	3.766%	$181.4037	$181.40	$181.40	$181.40
Purchase #3	$72.91	12.338%	$81.9056	$81.91	$81.90	$81.90
Purchase #4	$101.47	12.348%	$113.9995	$114.00	$114.00	$114.00
Purchase #5	$35.27	6.808%	$37.6712	$37.67	$37.65	$37.70
Purchase #6	$85.86	7.718%	$92.4867	$92.49	$92.50	$92.50
Purchase #7	$235.88	8.544%	$256.0336	$256.03	$256.05	$256.00
7 purchase totals =	$934.11		$1,020.1636	$1,020.16	$1,020.15	$1,020.20