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	$81.88	12.186%	$91.8579	$91.86	$91.85	$91.90
Purchase #2	$121.81	8.108%	$131.6864	$131.69	$131.70	$131.70
Purchase #3	$142.38	10.541%	$157.3883	$157.39	$157.40	$157.40
Purchase #4	$84.99	12.633%	$95.7268	$95.73	$95.75	$95.70
Purchase #5	$49.98	5.852%	$52.9048	$52.90	$52.90	$52.90
Purchase #6	$101.61	3.271%	$104.9337	$104.93	$104.95	$104.90
Purchase #7	$100.38	10.822%	$111.2431	$111.24	$111.25	$111.20
7 purchase totals =	$683.03		$745.7410	$745.74	$745.80	$745.70