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	$37.56	9.723%	$41.212	$41.21	$41.20	$41.20
Purchase #2	$179.42	5.793%	$189.8138	$189.81	$189.80	$189.80
Purchase #3	$103.34	8.212%	$111.8263	$111.83	$111.85	$111.80
Purchase #4	$33.96	10.537%	$37.5384	$37.54	$37.55	$37.50
Purchase #5	$221.53	12.848%	$249.9922	$249.99	$250.00	$250.00
Purchase #6	$213.29	12.707%	$240.3928	$240.39	$240.40	$240.40
Purchase #7	$150.99	7.860%	$162.8578	$162.86	$162.85	$162.90
7 purchase totals =	$940.09		$1,033.6333	$1,033.63	$1,033.65	$1,033.60