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	$118.86	5.842%	$125.8038	$125.80	$125.80	$125.80
Purchase #2	$63.78	6.295%	$67.795	$67.80	$67.80	$67.80
Purchase #3	$47.77	9.163%	$52.1472	$52.15	$52.15	$52.10
Purchase #4	$201.29	13.435%	$228.3333	$228.33	$228.35	$228.30
Purchase #5	$72.33	13.805%	$82.3152	$82.32	$82.30	$82.30
Purchase #6	$141.85	13.440%	$160.9146	$160.91	$160.90	$160.90
Purchase #7	$96.92	4.381%	$101.1661	$101.17	$101.15	$101.20
7 purchase totals =	$742.80		$818.4752	$818.48	$818.45	$818.40