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	$116.70	9.806%	$128.1436	$128.14	$128.15	$128.10
Purchase #2	$25.25	12.599%	$28.4312	$28.43	$28.45	$28.40
Purchase #3	$76.55	3.123%	$78.9407	$78.94	$78.95	$78.90
Purchase #4	$92.96	7.387%	$99.827	$99.83	$99.85	$99.80
Purchase #5	$232.43	3.242%	$239.9654	$239.97	$239.95	$240.00
Purchase #6	$104.73	4.863%	$109.823	$109.82	$109.80	$109.80
Purchase #7	$208.36	7.233%	$223.4307	$223.43	$223.45	$223.40
7 purchase totals =	$856.98		$908.5616	$908.56	$908.60	$908.40