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	$176.59	13.516%	$200.4579	$200.46	$200.45	$200.50
Purchase #2	$105.88	6.287%	$112.5367	$112.54	$112.55	$112.50
Purchase #3	$68.52	9.832%	$75.2569	$75.26	$75.25	$75.30
Purchase #4	$234.97	4.269%	$245.0009	$245.00	$245.00	$245.00
Purchase #5	$48.34	12.231%	$54.2525	$54.25	$54.25	$54.30
Purchase #6	$35.57	4.821%	$37.2848	$37.28	$37.30	$37.30
Purchase #7	$40.61	6.115%	$43.0933	$43.09	$43.10	$43.10
7 purchase totals =	$710.48		$767.8830	$767.88	$767.90	$768.00