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	$136.50	4.440%	$142.5606	$142.56	$142.55	$142.60
Purchase #2	$52.46	13.497%	$59.5405	$59.54	$59.55	$59.50
Purchase #3	$181.53	12.440%	$204.1123	$204.11	$204.10	$204.10
Purchase #4	$36.82	12.142%	$41.2907	$41.29	$41.30	$41.30
Purchase #5	$231.47	10.836%	$256.5521	$256.55	$256.55	$256.60
Purchase #6	$223.89	10.314%	$246.982	$246.98	$247.00	$247.00
Purchase #7	$222.56	12.246%	$249.8147	$249.81	$249.80	$249.80
7 purchase totals =	$1,085.23		$1,200.8529	$1,200.84	$1,200.85	$1,200.90