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	$157.38	4.380%	$164.2732	$164.27	$164.25	$164.30
Purchase #2	$112.46	9.270%	$122.885	$122.89	$122.90	$122.90
Purchase #3	$221.67	7.747%	$238.8428	$238.84	$238.85	$238.80
Purchase #4	$208.65	6.747%	$222.7276	$222.73	$222.75	$222.70
Purchase #5	$105.51	13.832%	$120.1041	$120.10	$120.10	$120.10
Purchase #6	$142.28	3.699%	$147.5429	$147.54	$147.55	$147.50
Purchase #7	$103.54	12.855%	$116.8501	$116.85	$116.85	$116.90
7 purchase totals =	$1,051.49		$1,133.2257	$1,133.22	$1,133.25	$1,133.20