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	$168.60	5.853%	$178.4682	$178.47	$178.45	$178.50
Purchase #2	$140.97	6.833%	$150.6025	$150.60	$150.60	$150.60
Purchase #3	$61.81	8.143%	$66.8432	$66.84	$66.85	$66.80
Purchase #4	$144.73	13.713%	$164.5768	$164.58	$164.60	$164.60
Purchase #5	$200.89	10.326%	$221.6339	$221.63	$221.65	$221.60
Purchase #6	$35.56	12.317%	$39.9399	$39.94	$39.95	$39.90
Purchase #7	$196.64	13.529%	$223.2434	$223.24	$223.25	$223.20
7 purchase totals =	$949.20		$1,045.3079	$1,045.30	$1,045.35	$1,045.20