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	$137.78	13.107%	$155.8388	$155.84	$155.85	$155.80
Purchase #2	$180.82	3.433%	$187.0276	$187.03	$187.05	$187.00
Purchase #3	$211.55	4.435%	$220.9322	$220.93	$220.95	$220.90
Purchase #4	$82.94	3.334%	$85.7052	$85.71	$85.70	$85.70
Purchase #5	$59.69	13.737%	$67.8896	$67.89	$67.90	$67.90
Purchase #6	$145.96	13.771%	$166.0602	$166.06	$166.05	$166.10
Purchase #7	$144.79	13.732%	$164.6726	$164.67	$164.65	$164.70
7 purchase totals =	$963.53		$1,048.1262	$1,048.13	$1,048.15	$1,048.10