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	$210.35	3.714%	$218.1624	$218.16	$218.15	$218.20
Purchase #2	$242.72	5.863%	$256.9507	$256.95	$256.95	$257.00
Purchase #3	$194.72	4.764%	$203.9965	$204.00	$204.00	$204.00
Purchase #4	$151.27	11.336%	$168.418	$168.42	$168.40	$168.40
Purchase #5	$37.41	13.873%	$42.5999	$42.60	$42.60	$42.60
Purchase #6	$123.65	13.206%	$139.9792	$139.98	$140.00	$140.00
Purchase #7	$53.64	5.648%	$56.6696	$56.67	$56.65	$56.70
7 purchase totals =	$1,013.76		$1,086.7763	$1,086.78	$1,086.75	$1,086.90