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	$130.67	6.611%	$139.3086	$139.31	$139.30	$139.30
Purchase #2	$180.82	8.662%	$196.4826	$196.48	$196.50	$196.50
Purchase #3	$40.78	12.500%	$45.8775	$45.88	$45.90	$45.90
Purchase #4	$167.79	8.385%	$181.8592	$181.86	$181.85	$181.90
Purchase #5	$162.33	7.193%	$174.0064	$174.01	$174.00	$174.00
Purchase #6	$208.83	6.691%	$222.8028	$222.80	$222.80	$222.80
Purchase #7	$176.45	7.551%	$189.7737	$189.77	$189.75	$189.80
7 purchase totals =	$1,067.67		$1,150.1108	$1,150.11	$1,150.10	$1,150.20