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	$111.81	3.454%	$115.6719	$115.67	$115.65	$115.70
Purchase #2	$40.64	4.690%	$42.546	$42.55	$42.55	$42.50
Purchase #3	$205.40	9.476%	$224.8637	$224.86	$224.85	$224.90
Purchase #4	$109.67	13.558%	$124.5391	$124.54	$124.55	$124.50
Purchase #5	$124.28	13.769%	$141.3921	$141.39	$141.40	$141.40
Purchase #6	$135.55	6.419%	$144.251	$144.25	$144.25	$144.30
Purchase #7	$238.75	8.680%	$259.4735	$259.47	$259.45	$259.50
7 purchase totals =	$966.10		$1,052.7373	$1,052.73	$1,052.70	$1,052.80