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	$57.69	6.803%	$61.6147	$61.61	$61.60	$61.60
Purchase #2	$96.63	13.339%	$109.5195	$109.52	$109.50	$109.50
Purchase #3	$55.83	11.292%	$62.1343	$62.13	$62.15	$62.10
Purchase #4	$121.44	9.804%	$133.346	$133.35	$133.35	$133.30
Purchase #5	$22.85	8.541%	$24.8016	$24.80	$24.80	$24.80
Purchase #6	$50.57	13.709%	$57.5026	$57.50	$57.50	$57.50
Purchase #7	$182.62	9.778%	$200.4766	$200.48	$200.50	$200.50
7 purchase totals =	$587.63		$649.3953	$649.39	$649.40	$649.30