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	$29.86	10.808%	$33.0873	$33.09	$33.10	$33.10
Purchase #2	$145.47	5.676%	$153.7269	$153.73	$153.75	$153.70
Purchase #3	$67.26	7.300%	$72.17	$72.17	$72.15	$72.20
Purchase #4	$22.26	6.508%	$23.7087	$23.71	$23.70	$23.70
Purchase #5	$61.70	5.112%	$64.8541	$64.85	$64.85	$64.90
Purchase #6	$117.67	4.848%	$123.3746	$123.37	$123.35	$123.40
Purchase #7	$154.47	5.202%	$162.5055	$162.51	$162.50	$162.50
7 purchase totals =	$598.69		$633.4271	$633.43	$633.40	$633.50