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	$208.31	6.526%	$221.9043	$221.90	$221.90	$221.90
Purchase #2	$147.95	11.441%	$164.877	$164.88	$164.90	$164.90
Purchase #3	$124.42	10.383%	$137.3385	$137.34	$137.35	$137.30
Purchase #4	$18.80	8.483%	$20.3948	$20.39	$20.40	$20.40
Purchase #5	$105.49	13.230%	$119.4463	$119.45	$119.45	$119.40
Purchase #6	$162.30	7.815%	$174.9837	$174.98	$175.00	$175.00
Purchase #7	$239.82	13.448%	$272.071	$272.07	$272.05	$272.10
7 purchase totals =	$1,007.09		$1,111.0156	$1,111.01	$1,111.05	$1,111.00