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	$149.29	5.775%	$157.9115	$157.91	$157.90	$157.90
Purchase #2	$54.36	9.551%	$59.5519	$59.55	$59.55	$59.60
Purchase #3	$113.48	3.503%	$117.4552	$117.46	$117.45	$117.50
Purchase #4	$249.54	6.209%	$265.0339	$265.03	$265.05	$265.00
Purchase #5	$134.78	5.395%	$142.0514	$142.05	$142.05	$142.10
Purchase #6	$180.44	10.264%	$198.9604	$198.96	$198.95	$199.00
Purchase #7	$175.99	8.203%	$190.4265	$190.43	$190.45	$190.40
7 purchase totals =	$1,057.88		$1,131.3908	$1,131.39	$1,131.40	$1,131.50