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	$69.93	3.685%	$72.5069	$72.51	$72.50	$72.50
Purchase #2	$169.46	13.185%	$191.8033	$191.80	$191.80	$191.80
Purchase #3	$119.47	12.558%	$134.473	$134.47	$134.45	$134.50
Purchase #4	$151.36	13.337%	$171.5469	$171.55	$171.55	$171.50
Purchase #5	$55.73	9.360%	$60.9463	$60.95	$60.95	$60.90
Purchase #6	$196.82	10.411%	$217.3109	$217.31	$217.30	$217.30
Purchase #7	$45.32	3.218%	$46.7784	$46.78	$46.80	$46.80
7 purchase totals =	$808.09		$895.3657	$895.37	$895.35	$895.30