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	$36.56	3.770%	$37.9383	$37.94	$37.95	$37.90
Purchase #2	$210.88	5.474%	$222.4236	$222.42	$222.40	$222.40
Purchase #3	$90.47	5.716%	$95.6413	$95.64	$95.65	$95.60
Purchase #4	$114.69	3.737%	$118.976	$118.98	$119.00	$119.00
Purchase #5	$162.80	11.779%	$181.9762	$181.98	$182.00	$182.00
Purchase #6	$39.98	3.364%	$41.3249	$41.32	$41.30	$41.30
Purchase #7	$211.49	9.478%	$231.535	$231.54	$231.55	$231.50
7 purchase totals =	$866.87		$929.8153	$929.82	$929.85	$929.70