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	$154.49	10.757%	$171.1085	$171.11	$171.10	$171.10
Purchase #2	$39.50	7.524%	$42.472	$42.47	$42.45	$42.50
Purchase #3	$198.40	6.553%	$211.4012	$211.40	$211.40	$211.40
Purchase #4	$153.30	7.332%	$164.54	$164.54	$164.55	$164.50
Purchase #5	$108.31	4.223%	$112.8839	$112.88	$112.90	$112.90
Purchase #6	$118.43	11.119%	$131.5982	$131.60	$131.60	$131.60
Purchase #7	$89.26	8.251%	$96.6248	$96.62	$96.60	$96.60
7 purchase totals =	$861.69		$930.6286	$930.62	$930.60	$930.60