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	$78.77	4.697%	$82.4698	$82.47	$82.45	$82.50
Purchase #2	$156.27	3.805%	$162.2161	$162.22	$162.20	$162.20
Purchase #3	$162.46	4.596%	$169.9267	$169.93	$169.95	$169.90
Purchase #4	$229.59	4.266%	$239.3843	$239.38	$239.40	$239.40
Purchase #5	$126.43	10.429%	$139.6154	$139.62	$139.60	$139.60
Purchase #6	$238.70	7.331%	$256.1991	$256.20	$256.20	$256.20
Purchase #7	$39.30	12.303%	$44.1351	$44.14	$44.15	$44.10
7 purchase totals =	$1,031.52		$1,093.9465	$1,093.96	$1,093.95	$1,093.90