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	$199.46	11.237%	$221.8733	$221.87	$221.85	$221.90
Purchase #2	$172.81	11.347%	$192.4188	$192.42	$192.40	$192.40
Purchase #3	$243.41	12.366%	$273.5101	$273.51	$273.50	$273.50
Purchase #4	$221.82	12.396%	$249.3168	$249.32	$249.30	$249.30
Purchase #5	$95.77	6.659%	$102.1473	$102.15	$102.15	$102.10
Purchase #6	$93.76	8.750%	$101.964	$101.96	$101.95	$102.00
Purchase #7	$49.87	11.595%	$55.6524	$55.65	$55.65	$55.70
7 purchase totals =	$1,076.90		$1,196.8827	$1,196.88	$1,196.80	$1,196.90