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	$72.99	3.299%	$75.3979	$75.40	$75.40	$75.40
Purchase #2	$86.79	8.738%	$94.3737	$94.37	$94.35	$94.40
Purchase #3	$231.44	4.393%	$241.6072	$241.61	$241.60	$241.60
Purchase #4	$157.56	13.200%	$178.3579	$178.36	$178.35	$178.40
Purchase #5	$190.39	4.769%	$199.4697	$199.47	$199.45	$199.50
Purchase #6	$68.31	6.565%	$72.7946	$72.79	$72.80	$72.80
Purchase #7	$54.35	9.260%	$59.3828	$59.38	$59.40	$59.40
7 purchase totals =	$861.83		$921.3838	$921.38	$921.35	$921.50