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	$72.92	3.592%	$75.5393	$75.54	$75.55	$75.50
Purchase #2	$162.93	12.228%	$182.8531	$182.85	$182.85	$182.90
Purchase #3	$211.88	10.863%	$234.8965	$234.90	$234.90	$234.90
Purchase #4	$45.90	12.323%	$51.5563	$51.56	$51.55	$51.60
Purchase #5	$243.44	13.710%	$276.8156	$276.82	$276.80	$276.80
Purchase #6	$59.60	13.346%	$67.5542	$67.55	$67.55	$67.60
Purchase #7	$130.55	4.656%	$136.6284	$136.63	$136.65	$136.60
7 purchase totals =	$927.22		$1,025.8434	$1,025.85	$1,025.85	$1,025.90