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	$133.66	6.192%	$141.9362	$141.94	$141.95	$141.90
Purchase #2	$226.77	5.240%	$238.6527	$238.65	$238.65	$238.70
Purchase #3	$85.59	5.622%	$90.4019	$90.40	$90.40	$90.40
Purchase #4	$70.48	4.718%	$73.8052	$73.81	$73.80	$73.80
Purchase #5	$72.53	13.219%	$82.1177	$82.12	$82.10	$82.10
Purchase #6	$226.80	5.439%	$239.1357	$239.14	$239.15	$239.10
Purchase #7	$195.58	11.255%	$217.5925	$217.59	$217.60	$217.60
7 purchase totals =	$1,011.41		$1,083.6419	$1,083.65	$1,083.65	$1,083.60