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	$103.75	5.477%	$109.4324	$109.43	$109.45	$109.40
Purchase #2	$66.32	9.464%	$72.5965	$72.60	$72.60	$72.60
Purchase #3	$220.84	13.507%	$250.6689	$250.67	$250.65	$250.70
Purchase #4	$173.28	10.225%	$190.9979	$191.00	$191.00	$191.00
Purchase #5	$238.92	11.470%	$266.3241	$266.32	$266.30	$266.30
Purchase #6	$195.83	3.400%	$202.4882	$202.49	$202.50	$202.50
Purchase #7	$216.77	5.588%	$228.8831	$228.88	$228.90	$228.90
7 purchase totals =	$1,215.71		$1,321.3911	$1,321.39	$1,321.40	$1,321.40