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	$136.67	3.471%	$141.4138	$141.41	$141.40	$141.40
Purchase #2	$26.38	6.311%	$28.0448	$28.04	$28.05	$28.00
Purchase #3	$188.34	13.601%	$213.9561	$213.96	$213.95	$214.00
Purchase #4	$78.83	9.816%	$86.568	$86.57	$86.55	$86.60
Purchase #5	$162.85	10.431%	$179.8369	$179.84	$179.85	$179.80
Purchase #6	$90.89	8.276%	$98.4121	$98.41	$98.40	$98.40
Purchase #7	$34.44	10.473%	$38.0469	$38.05	$38.05	$38.00
7 purchase totals =	$718.40		$786.2786	$786.28	$786.25	$786.20