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	$131.30	10.183%	$144.6703	$144.67	$144.65	$144.70
Purchase #2	$163.81	5.499%	$172.8179	$172.82	$172.80	$172.80
Purchase #3	$50.52	6.406%	$53.7563	$53.76	$53.75	$53.80
Purchase #4	$26.61	9.558%	$29.1534	$29.15	$29.15	$29.20
Purchase #5	$109.36	3.810%	$113.5266	$113.53	$113.55	$113.50
Purchase #6	$142.31	8.645%	$154.6127	$154.61	$154.60	$154.60
Purchase #7	$77.89	9.847%	$85.5598	$85.56	$85.55	$85.60
7 purchase totals =	$701.80		$754.0970	$754.10	$754.05	$754.20