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	$36.57	4.127%	$38.0792	$38.08	$38.10	$38.10
Purchase #2	$157.76	10.691%	$174.6261	$174.63	$174.65	$174.60
Purchase #3	$79.83	13.484%	$90.5943	$90.59	$90.60	$90.60
Purchase #4	$150.85	9.596%	$165.3256	$165.33	$165.35	$165.30
Purchase #5	$82.81	4.217%	$86.3021	$86.30	$86.30	$86.30
Purchase #6	$139.56	13.655%	$158.6169	$158.62	$158.60	$158.60
Purchase #7	$248.55	13.329%	$281.6792	$281.68	$281.70	$281.70
7 purchase totals =	$895.93		$995.2234	$995.23	$995.30	$995.20