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	$199.35	8.392%	$216.0795	$216.08	$216.10	$216.10
Purchase #2	$16.42	10.762%	$18.1871	$18.19	$18.20	$18.20
Purchase #3	$174.29	6.672%	$185.9186	$185.92	$185.90	$185.90
Purchase #4	$142.83	5.185%	$150.2357	$150.24	$150.25	$150.20
Purchase #5	$11.87	12.196%	$13.3177	$13.32	$13.30	$13.30
Purchase #6	$171.60	8.581%	$186.325	$186.33	$186.35	$186.30
Purchase #7	$218.57	9.222%	$238.7265	$238.73	$238.75	$238.70
7 purchase totals =	$934.93		$1,008.7901	$1,008.81	$1,008.85	$1,008.70