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	$89.82	8.636%	$97.5769	$97.58	$97.60	$97.60
Purchase #2	$197.80	5.698%	$209.0706	$209.07	$209.05	$209.10
Purchase #3	$116.63	10.448%	$128.8155	$128.82	$128.80	$128.80
Purchase #4	$123.38	9.312%	$134.8691	$134.87	$134.85	$134.90
Purchase #5	$184.37	7.583%	$198.3508	$198.35	$198.35	$198.40
Purchase #6	$141.71	10.128%	$156.0624	$156.06	$156.05	$156.10
Purchase #7	$90.29	4.171%	$94.056	$94.06	$94.05	$94.10
7 purchase totals =	$944.00		$1,018.8013	$1,018.81	$1,018.75	$1,019.00