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	$229.70	5.533%	$242.4093	$242.41	$242.40	$242.40
Purchase #2	$37.81	9.337%	$41.3403	$41.34	$41.35	$41.30
Purchase #3	$157.72	12.154%	$176.8893	$176.89	$176.90	$176.90
Purchase #4	$141.45	11.625%	$157.8936	$157.89	$157.90	$157.90
Purchase #5	$167.43	12.152%	$187.7761	$187.78	$187.80	$187.80
Purchase #6	$79.31	9.601%	$86.9246	$86.92	$86.90	$86.90
Purchase #7	$141.63	6.103%	$150.2737	$150.27	$150.25	$150.30
7 purchase totals =	$955.05		$1,043.5069	$1,043.50	$1,043.50	$1,043.50