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	$69.52	6.157%	$73.8003	$73.80	$73.80	$73.80
Purchase #2	$142.93	6.190%	$151.7774	$151.78	$151.80	$151.80
Purchase #3	$41.93	3.621%	$43.4483	$43.45	$43.45	$43.40
Purchase #4	$59.59	3.854%	$61.8866	$61.89	$61.90	$61.90
Purchase #5	$190.81	13.349%	$216.2812	$216.28	$216.30	$216.30
Purchase #6	$21.63	12.576%	$24.3502	$24.35	$24.35	$24.40
Purchase #7	$177.55	5.828%	$187.8976	$187.90	$187.90	$187.90
7 purchase totals =	$703.96		$759.4416	$759.45	$759.50	$759.50