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	$211.45	13.696%	$240.4102	$240.41	$240.40	$240.40
Purchase #2	$213.43	5.551%	$225.2775	$225.28	$225.30	$225.30
Purchase #3	$18.37	13.591%	$20.8667	$20.87	$20.85	$20.90
Purchase #4	$155.77	6.763%	$166.3047	$166.30	$166.30	$166.30
Purchase #5	$103.84	9.245%	$113.44	$113.44	$113.45	$113.40
Purchase #6	$214.83	10.524%	$237.4387	$237.44	$237.45	$237.40
Purchase #7	$199.91	11.798%	$223.4954	$223.50	$223.50	$223.50
7 purchase totals =	$1,117.60		$1,227.2332	$1,227.24	$1,227.25	$1,227.20