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	$190.86	9.292%	$208.5947	$208.59	$208.60	$208.60
Purchase #2	$42.45	13.811%	$48.3128	$48.31	$48.30	$48.30
Purchase #3	$164.71	10.503%	$182.0095	$182.01	$182.00	$182.00
Purchase #4	$190.96	4.714%	$199.9619	$199.96	$199.95	$200.00
Purchase #5	$112.84	6.711%	$120.4127	$120.41	$120.40	$120.40
Purchase #6	$136.98	10.150%	$150.8835	$150.88	$150.90	$150.90
Purchase #7	$131.48	7.196%	$140.9413	$140.94	$140.95	$140.90
7 purchase totals =	$970.28		$1,051.1164	$1,051.10	$1,051.10	$1,051.10