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	$71.54	9.103%	$78.0523	$78.05	$78.05	$78.10
Purchase #2	$13.27	4.602%	$13.8807	$13.88	$13.90	$13.90
Purchase #3	$91.64	13.411%	$103.9298	$103.93	$103.95	$103.90
Purchase #4	$100.98	10.401%	$111.4829	$111.48	$111.50	$111.50
Purchase #5	$40.40	13.197%	$45.7316	$45.73	$45.75	$45.70
Purchase #6	$165.91	13.438%	$188.205	$188.21	$188.20	$188.20
Purchase #7	$190.68	5.542%	$201.2475	$201.25	$201.25	$201.20
7 purchase totals =	$674.42		$742.5298	$742.53	$742.60	$742.50