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	$144.46	5.683%	$152.6697	$152.67	$152.65	$152.70
Purchase #2	$156.76	9.379%	$171.4625	$171.46	$171.45	$171.50
Purchase #3	$214.50	13.387%	$243.2151	$243.22	$243.20	$243.20
Purchase #4	$208.32	6.346%	$221.54	$221.54	$221.55	$221.50
Purchase #5	$179.32	11.119%	$199.2586	$199.26	$199.25	$199.30
Purchase #6	$247.46	7.455%	$265.9081	$265.91	$265.90	$265.90
Purchase #7	$152.90	7.424%	$164.2513	$164.25	$164.25	$164.30
7 purchase totals =	$1,303.72		$1,418.3053	$1,418.31	$1,418.25	$1,418.40