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	$164.25	12.820%	$185.3069	$185.31	$185.30	$185.30
Purchase #2	$154.31	12.643%	$173.8194	$173.82	$173.80	$173.80
Purchase #3	$136.67	7.222%	$146.5403	$146.54	$146.55	$146.50
Purchase #4	$197.59	13.300%	$223.8695	$223.87	$223.85	$223.90
Purchase #5	$47.69	4.562%	$49.8656	$49.87	$49.85	$49.90
Purchase #6	$110.31	10.483%	$121.8738	$121.87	$121.85	$121.90
Purchase #7	$164.33	6.845%	$175.5784	$175.58	$175.60	$175.60
7 purchase totals =	$975.15		$1,076.8539	$1,076.86	$1,076.80	$1,076.90