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	$85.49	4.820%	$89.6106	$89.61	$89.60	$89.60
Purchase #2	$54.91	6.479%	$58.4676	$58.47	$58.45	$58.50
Purchase #3	$211.43	11.554%	$235.8586	$235.86	$235.85	$235.90
Purchase #4	$47.71	6.803%	$50.9557	$50.96	$50.95	$51.00
Purchase #5	$99.63	10.528%	$110.119	$110.12	$110.10	$110.10
Purchase #6	$134.83	9.404%	$147.5094	$147.51	$147.50	$147.50
Purchase #7	$66.94	3.771%	$69.4643	$69.46	$69.45	$69.50
7 purchase totals =	$700.94		$761.9852	$761.99	$761.90	$762.10