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	$93.57	3.177%	$96.5427	$96.54	$96.55	$96.50
Purchase #2	$48.84	9.211%	$53.3387	$53.34	$53.35	$53.30
Purchase #3	$150.33	4.737%	$157.4511	$157.45	$157.45	$157.50
Purchase #4	$123.71	11.764%	$138.2632	$138.26	$138.25	$138.30
Purchase #5	$164.56	9.596%	$180.3512	$180.35	$180.35	$180.40
Purchase #6	$214.86	7.476%	$230.9229	$230.92	$230.90	$230.90
Purchase #7	$92.43	11.857%	$103.3894	$103.39	$103.40	$103.40
7 purchase totals =	$888.30		$960.2592	$960.25	$960.25	$960.30