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	$210.30	3.536%	$217.7362	$217.74	$217.75	$217.70
Purchase #2	$249.37	4.122%	$259.649	$259.65	$259.65	$259.60
Purchase #3	$40.81	11.135%	$45.3542	$45.35	$45.35	$45.40
Purchase #4	$84.62	12.588%	$95.272	$95.27	$95.25	$95.30
Purchase #5	$161.47	11.841%	$180.5897	$180.59	$180.60	$180.60
Purchase #6	$41.48	5.116%	$43.6021	$43.60	$43.60	$43.60
Purchase #7	$191.50	12.723%	$215.8645	$215.86	$215.85	$215.90
7 purchase totals =	$979.55		$1,058.0677	$1,058.06	$1,058.05	$1,058.10