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	$86.68	5.737%	$91.6528	$91.65	$91.65	$91.70
Purchase #2	$250.45	4.541%	$261.8229	$261.82	$261.80	$261.80
Purchase #3	$245.64	7.790%	$264.7754	$264.78	$264.80	$264.80
Purchase #4	$167.42	8.544%	$181.7244	$181.72	$181.70	$181.70
Purchase #5	$36.54	6.144%	$38.785	$38.79	$38.80	$38.80
Purchase #6	$217.43	7.767%	$234.3178	$234.32	$234.30	$234.30
Purchase #7	$25.83	7.555%	$27.7815	$27.78	$27.80	$27.80
7 purchase totals =	$1,029.99		$1,100.8598	$1,100.86	$1,100.85	$1,100.90