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	$110.55	11.767%	$123.5584	$123.56	$123.55	$123.60
Purchase #2	$94.43	8.272%	$102.2412	$102.24	$102.25	$102.20
Purchase #3	$34.89	5.794%	$36.9115	$36.91	$36.90	$36.90
Purchase #4	$79.82	13.798%	$90.8336	$90.83	$90.85	$90.80
Purchase #5	$201.71	10.170%	$222.2239	$222.22	$222.20	$222.20
Purchase #6	$242.27	7.767%	$261.0871	$261.09	$261.10	$261.10
Purchase #7	$228.56	7.237%	$245.1009	$245.10	$245.10	$245.10
7 purchase totals =	$992.23		$1,081.9566	$1,081.95	$1,081.95	$1,081.90