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	$174.68	6.298%	$185.6813	$185.68	$185.70	$185.70
Purchase #2	$220.38	10.673%	$243.9012	$243.90	$243.90	$243.90
Purchase #3	$72.41	8.477%	$78.5482	$78.55	$78.55	$78.50
Purchase #4	$174.40	12.426%	$196.0709	$196.07	$196.05	$196.10
Purchase #5	$43.52	13.634%	$49.4535	$49.45	$49.45	$49.50
Purchase #6	$23.67	12.436%	$26.6136	$26.61	$26.60	$26.60
Purchase #7	$230.42	12.447%	$259.1004	$259.10	$259.10	$259.10
7 purchase totals =	$939.48		$1,039.3691	$1,039.36	$1,039.35	$1,039.40