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	$214.32	4.575%	$224.1251	$224.13	$224.15	$224.10
Purchase #2	$67.32	6.645%	$71.7934	$71.79	$71.80	$71.80
Purchase #3	$85.71	4.654%	$89.6989	$89.70	$89.70	$89.70
Purchase #4	$165.70	13.211%	$187.5906	$187.59	$187.60	$187.60
Purchase #5	$19.93	3.461%	$20.6198	$20.62	$20.60	$20.60
Purchase #6	$186.79	10.334%	$206.0929	$206.09	$206.10	$206.10
Purchase #7	$109.37	5.573%	$115.4652	$115.47	$115.45	$115.50
7 purchase totals =	$849.14		$915.3859	$915.39	$915.40	$915.40