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	$46.83	10.718%	$51.8492	$51.85	$51.85	$51.80
Purchase #2	$70.56	4.732%	$73.8989	$73.90	$73.90	$73.90
Purchase #3	$110.90	11.201%	$123.3219	$123.32	$123.30	$123.30
Purchase #4	$25.66	11.537%	$28.6204	$28.62	$28.60	$28.60
Purchase #5	$126.75	8.818%	$137.9268	$137.93	$137.95	$137.90
Purchase #6	$86.91	10.527%	$96.059	$96.06	$96.05	$96.10
Purchase #7	$55.71	3.818%	$57.837	$57.84	$57.85	$57.80
7 purchase totals =	$523.32		$569.5132	$569.52	$569.50	$569.40