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	$233.60	9.337%	$255.4112	$255.41	$255.40	$255.40
Purchase #2	$28.58	13.826%	$32.5315	$32.53	$32.55	$32.50
Purchase #3	$57.61	3.271%	$59.4944	$59.49	$59.50	$59.50
Purchase #4	$90.80	9.313%	$99.2562	$99.26	$99.25	$99.30
Purchase #5	$124.73	3.341%	$128.8972	$128.90	$128.90	$128.90
Purchase #6	$170.63	13.646%	$193.9142	$193.91	$193.90	$193.90
Purchase #7	$177.55	10.143%	$195.5589	$195.56	$195.55	$195.60
7 purchase totals =	$883.50		$965.0636	$965.06	$965.05	$965.10