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	$140.82	9.103%	$153.6388	$153.64	$153.65	$153.60
Purchase #2	$151.33	4.809%	$158.6075	$158.61	$158.60	$158.60
Purchase #3	$37.33	12.600%	$42.0336	$42.03	$42.05	$42.00
Purchase #4	$160.44	13.832%	$182.6321	$182.63	$182.65	$182.60
Purchase #5	$168.38	5.628%	$177.8564	$177.86	$177.85	$177.90
Purchase #6	$240.57	12.503%	$270.6485	$270.65	$270.65	$270.60
Purchase #7	$65.29	3.218%	$67.391	$67.39	$67.40	$67.40
7 purchase totals =	$964.16		$1,052.8079	$1,052.81	$1,052.85	$1,052.70