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	$198.42	10.682%	$219.6152	$219.62	$219.60	$219.60
Purchase #2	$220.39	7.754%	$237.479	$237.48	$237.50	$237.50
Purchase #3	$39.47	6.492%	$42.0324	$42.03	$42.05	$42.00
Purchase #4	$11.71	5.179%	$12.3165	$12.32	$12.30	$12.30
Purchase #5	$152.72	6.409%	$162.5078	$162.51	$162.50	$162.50
Purchase #6	$79.96	6.595%	$85.2334	$85.23	$85.25	$85.20
Purchase #7	$62.88	6.547%	$66.9968	$67.00	$67.00	$67.00
7 purchase totals =	$765.55		$826.1811	$826.19	$826.20	$826.10