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	$196.32	10.234%	$216.4114	$216.41	$216.40	$216.40
Purchase #2	$173.34	6.337%	$184.3246	$184.32	$184.30	$184.30
Purchase #3	$55.43	7.831%	$59.7707	$59.77	$59.75	$59.80
Purchase #4	$205.80	4.756%	$215.5878	$215.59	$215.60	$215.60
Purchase #5	$228.38	5.776%	$241.5712	$241.57	$241.55	$241.60
Purchase #6	$226.99	6.243%	$241.161	$241.16	$241.15	$241.20
Purchase #7	$100.76	13.781%	$114.6457	$114.65	$114.65	$114.60
7 purchase totals =	$1,187.02		$1,273.4724	$1,273.47	$1,273.40	$1,273.50