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	$42.55	5.856%	$45.0417	$45.04	$45.05	$45.00
Purchase #2	$112.82	13.515%	$128.0676	$128.07	$128.05	$128.10
Purchase #3	$200.72	6.181%	$213.1265	$213.13	$213.15	$213.10
Purchase #4	$132.53	3.665%	$137.3872	$137.39	$137.40	$137.40
Purchase #5	$215.36	4.810%	$225.7188	$225.72	$225.70	$225.70
Purchase #6	$144.55	4.155%	$150.5561	$150.56	$150.55	$150.60
Purchase #7	$73.66	6.437%	$78.4015	$78.40	$78.40	$78.40
7 purchase totals =	$922.19		$978.2994	$978.31	$978.30	$978.30