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	$245.46	9.548%	$268.8965	$268.90	$268.90	$268.90
Purchase #2	$49.68	11.519%	$55.4026	$55.40	$55.40	$55.40
Purchase #3	$30.44	12.846%	$34.3503	$34.35	$34.35	$34.40
Purchase #4	$44.53	3.105%	$45.9127	$45.91	$45.90	$45.90
Purchase #5	$160.80	4.747%	$168.4332	$168.43	$168.45	$168.40
Purchase #6	$210.37	5.360%	$221.6458	$221.65	$221.65	$221.60
Purchase #7	$218.61	13.713%	$248.588	$248.59	$248.60	$248.60
7 purchase totals =	$959.89		$1,043.2291	$1,043.23	$1,043.25	$1,043.20