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	$243.88	10.490%	$269.463	$269.46	$269.45	$269.50
Purchase #2	$174.89	4.320%	$182.4452	$182.45	$182.45	$182.40
Purchase #3	$130.73	6.336%	$139.0131	$139.01	$139.00	$139.00
Purchase #4	$92.90	13.498%	$105.4396	$105.44	$105.45	$105.40
Purchase #5	$28.92	13.236%	$32.7479	$32.75	$32.75	$32.70
Purchase #6	$116.97	12.220%	$131.2637	$131.26	$131.25	$131.30
Purchase #7	$65.59	11.321%	$73.0154	$73.02	$73.00	$73.00
7 purchase totals =	$853.88		$933.3879	$933.39	$933.35	$933.30