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	$47.86	9.348%	$52.334	$52.33	$52.35	$52.30
Purchase #2	$151.31	3.364%	$156.4001	$156.40	$156.40	$156.40
Purchase #3	$42.26	12.172%	$47.4039	$47.40	$47.40	$47.40
Purchase #4	$151.59	13.330%	$171.7969	$171.80	$171.80	$171.80
Purchase #5	$100.94	4.309%	$105.2895	$105.29	$105.30	$105.30
Purchase #6	$11.76	12.571%	$13.2383	$13.24	$13.25	$13.20
Purchase #7	$154.31	5.313%	$162.5085	$162.51	$162.50	$162.50
7 purchase totals =	$660.03		$708.9712	$708.97	$709.00	$708.90