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	$137.62	12.208%	$154.4206	$154.42	$154.40	$154.40
Purchase #2	$191.56	4.609%	$200.389	$200.39	$200.40	$200.40
Purchase #3	$71.26	3.475%	$73.7363	$73.74	$73.75	$73.70
Purchase #4	$127.38	6.765%	$135.9973	$136.00	$136.00	$136.00
Purchase #5	$97.61	12.569%	$109.8786	$109.88	$109.90	$109.90
Purchase #6	$142.29	4.179%	$148.2363	$148.24	$148.25	$148.20
Purchase #7	$215.60	10.762%	$238.8029	$238.80	$238.80	$238.80
7 purchase totals =	$983.32		$1,061.4610	$1,061.47	$1,061.50	$1,061.40