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	$59.32	3.395%	$61.3339	$61.33	$61.35	$61.30
Purchase #2	$123.26	6.705%	$131.5246	$131.52	$131.50	$131.50
Purchase #3	$62.57	9.545%	$68.5423	$68.54	$68.55	$68.50
Purchase #4	$171.71	11.440%	$191.3536	$191.35	$191.35	$191.40
Purchase #5	$28.51	3.553%	$29.523	$29.52	$29.50	$29.50
Purchase #6	$209.96	7.435%	$225.5705	$225.57	$225.55	$225.60
Purchase #7	$170.35	5.659%	$179.9901	$179.99	$180.00	$180.00
7 purchase totals =	$825.68		$887.8380	$887.82	$887.80	$887.80