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	$194.52	7.720%	$209.5369	$209.54	$209.55	$209.50
Purchase #2	$130.97	8.846%	$142.5556	$142.56	$142.55	$142.60
Purchase #3	$54.31	13.210%	$61.4844	$61.48	$61.50	$61.50
Purchase #4	$164.95	5.795%	$174.5089	$174.51	$174.50	$174.50
Purchase #5	$182.96	4.259%	$190.7523	$190.75	$190.75	$190.80
Purchase #6	$232.29	3.407%	$240.2041	$240.20	$240.20	$240.20
Purchase #7	$14.80	5.376%	$15.5956	$15.60	$15.60	$15.60
7 purchase totals =	$974.80		$1,034.6378	$1,034.64	$1,034.65	$1,034.70