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	$67.33	6.273%	$71.5536	$71.55	$71.55	$71.60
Purchase #2	$222.72	8.171%	$240.9185	$240.92	$240.90	$240.90
Purchase #3	$123.33	12.321%	$138.5255	$138.53	$138.55	$138.50
Purchase #4	$141.25	6.440%	$150.3465	$150.35	$150.35	$150.30
Purchase #5	$183.96	12.104%	$206.2265	$206.23	$206.25	$206.20
Purchase #6	$248.25	3.259%	$256.3405	$256.34	$256.35	$256.30
Purchase #7	$105.80	10.487%	$116.8952	$116.90	$116.90	$116.90
7 purchase totals =	$1,092.64		$1,180.8063	$1,180.82	$1,180.85	$1,180.70