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	$99.47	10.153%	$109.5692	$109.57	$109.55	$109.60
Purchase #2	$231.60	6.805%	$247.3604	$247.36	$247.35	$247.40
Purchase #3	$67.96	6.117%	$72.1171	$72.12	$72.10	$72.10
Purchase #4	$166.28	7.575%	$178.8757	$178.88	$178.90	$178.90
Purchase #5	$71.37	7.710%	$76.8726	$76.87	$76.85	$76.90
Purchase #6	$13.90	4.571%	$14.5354	$14.54	$14.55	$14.50
Purchase #7	$61.41	7.614%	$66.0858	$66.09	$66.10	$66.10
7 purchase totals =	$711.99		$765.4162	$765.43	$765.40	$765.50