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	$49.64	9.652%	$54.4313	$54.43	$54.45	$54.40
Purchase #2	$213.45	12.484%	$240.0971	$240.10	$240.10	$240.10
Purchase #3	$156.60	13.346%	$177.4998	$177.50	$177.50	$177.50
Purchase #4	$89.62	8.195%	$96.9644	$96.96	$96.95	$97.00
Purchase #5	$55.50	11.277%	$61.7587	$61.76	$61.75	$61.80
Purchase #6	$79.79	4.538%	$83.4109	$83.41	$83.40	$83.40
Purchase #7	$37.90	7.289%	$40.6625	$40.66	$40.65	$40.70
7 purchase totals =	$682.50		$754.8247	$754.82	$754.80	$754.90