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	$71.59	7.252%	$76.7817	$76.78	$76.80	$76.80
Purchase #2	$169.60	9.359%	$185.4729	$185.47	$185.45	$185.50
Purchase #3	$43.37	3.672%	$44.9625	$44.96	$44.95	$45.00
Purchase #4	$83.89	6.751%	$89.5534	$89.55	$89.55	$89.60
Purchase #5	$81.94	5.777%	$86.6737	$86.67	$86.65	$86.70
Purchase #6	$40.83	7.326%	$43.8212	$43.82	$43.80	$43.80
Purchase #7	$192.25	4.595%	$201.0839	$201.08	$201.10	$201.10
7 purchase totals =	$683.47		$728.3493	$728.33	$728.30	$728.50