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	$144.61	6.165%	$153.5252	$153.53	$153.55	$153.50
Purchase #2	$127.37	9.152%	$139.0269	$139.03	$139.05	$139.00
Purchase #3	$249.34	7.121%	$267.0955	$267.10	$267.10	$267.10
Purchase #4	$138.53	4.427%	$144.6627	$144.66	$144.65	$144.70
Purchase #5	$40.47	5.281%	$42.6072	$42.61	$42.60	$42.60
Purchase #6	$123.67	10.499%	$136.6541	$136.65	$136.65	$136.70
Purchase #7	$172.45	11.598%	$192.4508	$192.45	$192.45	$192.50
7 purchase totals =	$996.44		$1,076.0224	$1,076.03	$1,076.05	$1,076.10