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	$238.80	10.778%	$264.5379	$264.54	$264.55	$264.50
Purchase #2	$222.76	13.808%	$253.5187	$253.52	$253.50	$253.50
Purchase #3	$75.60	11.715%	$84.4565	$84.46	$84.45	$84.50
Purchase #4	$40.71	4.542%	$42.559	$42.56	$42.55	$42.60
Purchase #5	$157.42	13.541%	$178.7362	$178.74	$178.75	$178.70
Purchase #6	$174.55	5.703%	$184.5046	$184.50	$184.50	$184.50
Purchase #7	$29.57	8.782%	$32.1668	$32.17	$32.15	$32.20
7 purchase totals =	$939.41		$1,040.4797	$1,040.49	$1,040.45	$1,040.50