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	$58.47	9.141%	$63.8147	$63.81	$63.80	$63.80
Purchase #2	$242.94	7.517%	$261.2018	$261.20	$261.20	$261.20
Purchase #3	$131.45	3.653%	$136.2519	$136.25	$136.25	$136.30
Purchase #4	$51.65	5.230%	$54.3513	$54.35	$54.35	$54.40
Purchase #5	$196.64	13.376%	$222.9426	$222.94	$222.95	$222.90
Purchase #6	$30.42	4.261%	$31.7162	$31.72	$31.70	$31.70
Purchase #7	$145.86	11.164%	$162.1438	$162.14	$162.15	$162.10
7 purchase totals =	$857.43		$932.4223	$932.41	$932.40	$932.40