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	$109.96	3.119%	$113.3897	$113.39	$113.40	$113.40
Purchase #2	$168.51	12.447%	$189.4844	$189.48	$189.50	$189.50
Purchase #3	$233.25	9.699%	$255.8729	$255.87	$255.85	$255.90
Purchase #4	$193.88	7.740%	$208.8863	$208.89	$208.90	$208.90
Purchase #5	$182.49	6.525%	$194.3975	$194.40	$194.40	$194.40
Purchase #6	$168.39	7.837%	$181.5867	$181.59	$181.60	$181.60
Purchase #7	$141.30	11.460%	$157.493	$157.49	$157.50	$157.50
7 purchase totals =	$1,197.78		$1,301.1105	$1,301.11	$1,301.15	$1,301.20