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	$104.46	7.476%	$112.2694	$112.27	$112.25	$112.30
Purchase #2	$244.54	7.310%	$262.4159	$262.42	$262.40	$262.40
Purchase #3	$88.43	12.715%	$99.6739	$99.67	$99.65	$99.70
Purchase #4	$150.72	10.869%	$167.1018	$167.10	$167.10	$167.10
Purchase #5	$205.68	12.280%	$230.9375	$230.94	$230.95	$230.90
Purchase #6	$215.78	8.675%	$234.4989	$234.50	$234.50	$234.50
Purchase #7	$156.38	6.554%	$166.6291	$166.63	$166.65	$166.60
7 purchase totals =	$1,165.99		$1,273.5265	$1,273.53	$1,273.50	$1,273.50