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	$55.36	9.119%	$60.4083	$60.41	$60.40	$60.40
Purchase #2	$78.30	5.780%	$82.8257	$82.83	$82.85	$82.80
Purchase #3	$34.42	10.339%	$37.9787	$37.98	$38.00	$38.00
Purchase #4	$42.58	7.796%	$45.8995	$45.90	$45.90	$45.90
Purchase #5	$189.41	3.497%	$196.0337	$196.03	$196.05	$196.00
Purchase #6	$245.81	5.333%	$258.919	$258.92	$258.90	$258.90
Purchase #7	$121.36	4.606%	$126.9498	$126.95	$126.95	$126.90
7 purchase totals =	$767.24		$809.0147	$809.02	$809.05	$808.90