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	$208.91	12.521%	$235.0676	$235.07	$235.05	$235.10
Purchase #2	$249.71	7.724%	$268.9976	$269.00	$269.00	$269.00
Purchase #3	$119.90	9.649%	$131.4692	$131.47	$131.45	$131.50
Purchase #4	$54.30	13.532%	$61.6479	$61.65	$61.65	$61.60
Purchase #5	$152.61	6.412%	$162.3954	$162.40	$162.40	$162.40
Purchase #6	$39.52	10.874%	$43.8174	$43.82	$43.80	$43.80
Purchase #7	$161.35	8.172%	$174.5355	$174.54	$174.55	$174.50
7 purchase totals =	$986.30		$1,077.9306	$1,077.95	$1,077.90	$1,077.90