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	$148.46	12.223%	$166.6063	$166.61	$166.60	$166.60
Purchase #2	$90.61	9.517%	$99.2334	$99.23	$99.25	$99.20
Purchase #3	$225.65	8.633%	$245.1304	$245.13	$245.15	$245.10
Purchase #4	$68.82	5.705%	$72.7462	$72.75	$72.75	$72.70
Purchase #5	$70.47	5.136%	$74.0893	$74.09	$74.10	$74.10
Purchase #6	$211.85	7.157%	$227.0121	$227.01	$227.00	$227.00
Purchase #7	$168.93	12.618%	$190.2456	$190.25	$190.25	$190.20
7 purchase totals =	$984.79		$1,075.0633	$1,075.07	$1,075.10	$1,074.90