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	$98.75	12.844%	$111.4335	$111.43	$111.45	$111.40
Purchase #2	$174.37	6.339%	$185.4233	$185.42	$185.40	$185.40
Purchase #3	$74.38	5.441%	$78.427	$78.43	$78.45	$78.40
Purchase #4	$131.41	13.152%	$148.693	$148.69	$148.70	$148.70
Purchase #5	$86.50	9.604%	$94.8075	$94.81	$94.80	$94.80
Purchase #6	$133.54	3.155%	$137.7532	$137.75	$137.75	$137.80
Purchase #7	$165.73	10.751%	$183.5476	$183.55	$183.55	$183.50
7 purchase totals =	$864.68		$940.0851	$940.08	$940.10	$940.00