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	$240.29	10.636%	$265.8472	$265.85	$265.85	$265.80
Purchase #2	$88.91	4.109%	$92.5633	$92.56	$92.55	$92.60
Purchase #3	$48.48	12.575%	$54.5764	$54.58	$54.60	$54.60
Purchase #4	$51.60	5.592%	$54.4855	$54.49	$54.50	$54.50
Purchase #5	$24.69	9.478%	$27.0301	$27.03	$27.05	$27.00
Purchase #6	$94.29	6.437%	$100.3594	$100.36	$100.35	$100.40
Purchase #7	$165.38	5.271%	$174.0972	$174.10	$174.10	$174.10
7 purchase totals =	$713.64		$768.9591	$768.97	$769.00	$769.00