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	$158.25	13.242%	$179.2055	$179.21	$179.20	$179.20
Purchase #2	$47.92	7.407%	$51.4694	$51.47	$51.45	$51.50
Purchase #3	$67.79	5.813%	$71.7306	$71.73	$71.75	$71.70
Purchase #4	$212.42	13.834%	$241.8062	$241.81	$241.80	$241.80
Purchase #5	$152.59	10.615%	$168.7874	$168.79	$168.80	$168.80
Purchase #6	$192.46	11.590%	$214.7661	$214.77	$214.75	$214.80
Purchase #7	$194.34	3.372%	$200.8931	$200.89	$200.90	$200.90
7 purchase totals =	$1,025.77		$1,128.6583	$1,128.67	$1,128.65	$1,128.70