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	$84.93	7.705%	$91.4739	$91.47	$91.45	$91.50
Purchase #2	$64.55	11.786%	$72.1579	$72.16	$72.15	$72.20
Purchase #3	$83.70	9.225%	$91.4213	$91.42	$91.40	$91.40
Purchase #4	$60.73	4.446%	$63.4301	$63.43	$63.45	$63.40
Purchase #5	$177.82	3.518%	$184.0757	$184.08	$184.10	$184.10
Purchase #6	$183.43	12.382%	$206.1423	$206.14	$206.15	$206.10
Purchase #7	$177.78	12.672%	$200.3083	$200.31	$200.30	$200.30
7 purchase totals =	$832.94		$909.0095	$909.01	$909.00	$909.00