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	$63.73	11.619%	$71.1348	$71.13	$71.15	$71.10
Purchase #2	$39.77	13.308%	$45.0626	$45.06	$45.05	$45.10
Purchase #3	$48.90	6.321%	$51.991	$51.99	$52.00	$52.00
Purchase #4	$164.49	13.662%	$186.9626	$186.96	$186.95	$187.00
Purchase #5	$60.27	12.209%	$67.6284	$67.63	$67.65	$67.60
Purchase #6	$25.51	7.278%	$27.3666	$27.37	$27.35	$27.40
Purchase #7	$93.67	13.117%	$105.9567	$105.96	$105.95	$106.00
7 purchase totals =	$496.34		$556.1027	$556.10	$556.10	$556.20