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	$72.96	5.260%	$76.7977	$76.80	$76.80	$76.80
Purchase #2	$50.55	10.695%	$55.9563	$55.96	$55.95	$56.00
Purchase #3	$236.34	5.112%	$248.4217	$248.42	$248.40	$248.40
Purchase #4	$248.75	10.710%	$275.3911	$275.39	$275.40	$275.40
Purchase #5	$40.63	5.667%	$42.9325	$42.93	$42.95	$42.90
Purchase #6	$15.35	10.121%	$16.9036	$16.90	$16.90	$16.90
Purchase #7	$222.65	7.296%	$238.8945	$238.89	$238.90	$238.90
7 purchase totals =	$887.23		$955.2974	$955.29	$955.30	$955.30