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	$230.83	11.217%	$256.7222	$256.72	$256.70	$256.70
Purchase #2	$110.85	13.313%	$125.6075	$125.61	$125.60	$125.60
Purchase #3	$134.41	5.384%	$141.6466	$141.65	$141.65	$141.60
Purchase #4	$116.87	12.567%	$131.5571	$131.56	$131.55	$131.60
Purchase #5	$57.86	7.150%	$61.997	$62.00	$62.00	$62.00
Purchase #6	$164.56	10.600%	$182.0034	$182.00	$182.00	$182.00
Purchase #7	$170.89	11.144%	$189.934	$189.93	$189.95	$189.90
7 purchase totals =	$986.27		$1,089.4678	$1,089.47	$1,089.45	$1,089.40